Systems and methods for OFDM channelization

ABSTRACT

Systems and methods for OFDM channelization are provided that allow for the coexistence of sub-band channels and diversity channels. Methods of defining diversity sub-channels and sub-band sub-channels are provided and systematic channel definition and labeling schemes are provided.

PRIORITY CLAIM

This application is a continuation of and claims the benefit of priorityfrom U.S. patent application Ser. No. 13/588,674, entitled “Systems andMethods for OFDM Channelization” and filed on Aug. 17, 2012 (issuing asU.S. Pat. No. 8,842,514 on Sep. 23, 2014), which is a continuation ofand claims the benefit of priority from U.S. patent application Ser. No.11/887,114, entitled “Systems and Methods for OFDM Channelization” andfiled on Sep. 25, 2007 (now issued as U.S. Pat. No. 8,274,880 on Sep.25, 2012), which is a National Stage application from InternationalApplication Serial No. PCT/CA2006/000463, entitled “Systems and Methodsfor OFDM Channelization” and filed on Mar. 30, 2006, which claims thebenefit of priority from five (5) U.S. Provisional Patent ApplicationSer. Nos. 60/666,548 filed on Mar. 30, 2005; 60/710,527 filed on Aug.23, 2005; 60/728,845 filed on Oct. 21, 2005; 60/741,923 filed on Dec. 2,2005; 60/751,101 filed on Dec. 16, 2005, all of which are fullyincorporated herein by reference for all purposes to the extent notinconsistent with this application.

BACKGROUND

1. Field of the Application

The present invention relates to channelization systems and methods foruse in OFDM (orthogonal frequency division multiplexing) systems, suchas OFDM wireless networks.

2. Background of the Disclosure

Conventional OFDM systems accommodate slow moving mobile stations in amanner that takes advantage of the fact that it is possible to track thefading in the frequency domain as well as the time domain. In order totake advantage of the slowly changing channel, sub-band scheduling isperformed to assign a contiguous set of sub-carriers to each mobilestation. In this case, each sub-band mobile station typically reportsthe carrier to interference ratio (CIR) for each sub-band or only thebest sub-bands, where the number of bands to report is specified by thebase station.

Conventional OFDM systems accommodate fast moving mobile stations aswell. When a mobile station is moving too fast to perform channelsensitive scheduling, sub-carriers are assigned that are distributedover the entire bandwidth. In this case, the mobile station reports afull band CIR rather than a sub-band CIR.

The conventional approach to handling both slow moving mobile stationsand fast moving mobile stations has been to have some transmissionperiods dedicated to slow moving mobile stations, and to have othertransmission periods dedicated to fast moving mobile stations. Anexample of this is shown in FIG. 34 where the breakdown between resourceallocation for slow moving mobile stations and fast moving stations isshown with frequency on the vertical access 10, and time on thehorizontal axis 12. During some time intervals 14, the entire frequencyband is used to support channels with distributed sub-carriers, whileother time intervals 15 are used to support channels that areimplemented using sub-bands.

SUMMARY

According to one broad aspect, the invention provides a methodcomprising: transmitting OFDM symbols using a plurality of sub-carrierswithin an OFDM band; the OFDM symbols collectively containing diversitychannels and sub-band channels, each diversity channel utilizing aplurality of sub-carriers distributed across the OFDM band, and eachsub-band channel utilizing a contiguous set of sub-carriers within theOFDM band; at least some of the OFDM symbols simultaneously includingsub-carriers utilized by a sub-band channel and sub-carriers utilized bya diversity channel.

In some embodiments, the method further comprises: sub-dividing theplurality of sub-carriers into resource blocks, each resource blockcomprising a fixed number of contiguous sub-carriers over at least oneOFDM symbol duration; using each resource block in its entirety for oneof sub-band channel use or distributed channel use.

In some embodiments, the method further comprises: assigning eachresource block to either sub-band channel use or distributed channel usein a manner that is statically defined.

In some embodiments, the method further comprises: assigning eachresource block to either sub-band channel use or distributed channel ina manner that changes over time.

In some embodiments, the method further comprises: transmitting at leastone reference OFDM symbol for each fixed size set of traffic OFDMsymbols.

In some embodiments, each diversity channel comprises a plurality ofresource blocks spaced in frequency.

In some embodiments, the plurality of resource blocks spaced infrequency for a given diversity channel are simultaneously transmitted.

In some embodiments, the plurality of resource blocks spaced infrequency for a given diversity channel are transmitted during differentOFDM symbols.

In some embodiments, transmitting OFDM symbols using a plurality ofsub-carriers within an OFDM band is performed for each of a plurality ofantennas, the method further comprising: for each antenna, transmittinga respective set of scattered pilots, the sets of scattered pilots beingtransmitted so as not to interfere with each other.

In some embodiments, the method further comprises: for each antenna,transmitting at least one reference OFDM symbol; and for each fixed sizeset of traffic OFDM symbols, the scattered pilots being transmittedduring the reference symbol.

In some embodiments, the method further comprises transmitting at leastone reference OFDM symbol for each fixed size set of traffic; and foreach antenna transmitting some of the respective set of scattered pilotsduring the reference symbol and some of the scattered pilots duringtraffic symbols.

In some embodiments, the scattered pilots are inserted in a diamondshaped lattice pattern for each antenna.

In some embodiments, the method further comprises: defining a slot tocontain an N×M resource block space by dividing the plurality of OFDMsub-carriers into N≧2 sub-bands in frequency transmitted over M≧1sub-slots in time, each sub-slot containing L≧1 OFDM symbol; allocatingeach resource block in its entirety for one of diversity channel use orsub-band channel use.

In some embodiments, the method further comprises: for each slot,allocating resource blocks for sub-band channel use first, andallocating remaining resource blocks for diversity channel use.

In some embodiments, the method comprises: for each slot, defining a setof diversity sub-channels using sub-carriers of resource blocks leftover after sub-band channel assignment, and assigning each diversitychannel to be transmitted during the slot at least one diversitysub-channel.

In some embodiments, the diversity sub-channels are systematicallydefined such that given a set of resource blocks left over aftersub-band channel assignment, an identical set of diversity sub-channelswill always result.

In some embodiments, diversity sub-channels are assigned to diversitychannels using a sub-channelization tree having multiple levels, with afirst level in the tree comprising a plurality of nodes eachrepresenting a single diversity sub-channel, and each subsequent levelin the tree comprising one or more nodes, each node in a subsequentlevel combining at least two nodes of a previous level and representingall sub-channels represented by the at least two nodes of the previouslevel.

In some embodiments, each diversity channel comprises a set of one ormore diversity sub-channels represented by a respective single node inthe sub-channelization tree.

In some embodiments, the method further comprises: signaling diversitychannel definitions by sending information associating each diversitychannel with the respective single node in the sub-channelization tree,and sending a user identifier for each diversity channel.

In some embodiments, each diversity sub-channel comprises: at least onesub-carrier in corresponding sub-carrier positions within each resourceblock available for diversity channel use.

In some embodiments, diversity sub-channels are defined using asub-channelization tree based on sub-carriers within a single sub-bandleftover-space-wise sub-channelization.

In some embodiments, defining a set of diversity sub-channels usingsub-carriers of resource blocks left over after sub-band channelassignment comprises performing leftover-space-wise sub-channelization.

In some embodiments, diversity sub-channels are defined using asub-channelization tree based on all sub-carriers available in theresource blocks left over after sub-band channel assignment in a givenslot, and diversity channels are assigned to be transmitted on diversitysub-channels on a slot-wise basis.

In some embodiments, diversity sub-channels are defined using asub-channelization tree based on all sub-carriers available in theresource blocks left over after sub-band channel assignment in a givensub-slot, and diversity channels are assigned to sub-channels on asub-slot-wise basis.

In some embodiments, each diversity sub-channel includes a respectiveset of OFDM sub-carriers over multiple consecutive OFDM symbols.

In some embodiments, each diversity sub-channel is transmitted overmultiple OFDM symbols, and comprises a respective set of OFDMsub-carriers that changes in a systematic manner within the multipleOFDM symbols.

In some embodiments, the method further comprises: sending signalinginformation that indicates which resource blocks are assigned tosub-band channels and which blocks are available to diversity channels.

In some embodiments, sending signaling information comprises: sending atwo dimensional bitmap that indicates for the N×M resource block spacewhich resource blocks are assigned to sub-band channels and which blocksare available to diversity channels.

In some embodiments, sending signaling information comprises: sending aone-dimensional bit map containing a single bit indicating for eachsub-band whether or not sub-band channels are to be included in thatsub-band; for each one bit in the one-dimensional bit map, sendinginformation that identifies a number of users, and for each user, startsub-slot index, and number of sub-slots.

In some embodiments, the method further comprises: assigning a uniqueregion identifier to each resource block, and sending the regionidentifier to indicate that the region is being used for a sub-bandchannel.

In some embodiments, the method further comprises: for each sub-bandchannel and each diversity channel, sending a respective useridentifier.

In some embodiments, defining a set of diversity sub-channels usingsub-carriers of resource blocks left over after sub-band channelassignment comprises: for each slot, defining a respective set ofdiversity sub-channels that use the available sub-carriers for the slot;combining all of the sub-channels into a sub-channelization tree thatdefines allowable combinations of the sub-channels.

In some embodiments, the method further comprises: using a time domaintree to identify consecutive OFDM symbols within a slot; using afrequency domain tree to identify contiguous sub-bands; defining eachsub-band channel using a combination of the time domain tree and thefrequency domain tree.

In some embodiments, the time domain tree identifies consecutive symbolswithin a slot always including a first symbol within the slot.

In some embodiments, the method further comprises defining names foreach possible sub-band channel by performing one of: assigning a regionID to each node in the time domain tree and assigning a region ID toeach node in the frequency domain tree; assigning a region ID to eachnode in the time domain tree and using a bit map to identify nodes inthe frequency domain tree; using a bit map to identify nodes in the timedomain tree, and assigning a region ID to each node in the frequencydomain tree; using a first bit map to identify nodes in the time domaintree, and using a second bit map to identify nodes in the frequencydomain tree; using a bit map to identify each possible time domain treenode plus frequency domain tree node combination; assigning a region IDto each time domain tree node plus frequency domain tree nodecombination.

In some embodiments, the method further comprises: identifying sub-bandchannels by: sending information that identifies which resource blocksare available for sub-band channels; using a systematic namingconvention to name each permutation of one or more contiguous sub-bandsover one or more consecutive sub-slots; for each sub-band channel,transmitting a user identifier and a name from the systematic namingconvention that identifies the particular permutation of one or morecontiguous sub-bands over one or more consecutive sub-slots assigned tothat user.

In some embodiments, sending information that identifies which resourceblocks are available for sub-band channels comprises sending a bit map.

In some embodiments, the method comprises: defining sub-bandsub-channels using all of the plurality of OFDM sub-carriers; definingdiversity sub-channels using all of the plurality of OFDM sub-carriers;assigning each sub-band channel one or more sub-band sub-channels;assigning each diversity sub-channel one or more diversity sub-channels.

In some embodiments, the method further comprises: where there is aconflict between a sub-band channel and a diversity channel on a givensub-carrier, sending the sub-band channel on the sub-carrier.

In some embodiments, the method further comprises: using a sub-bandsub-channelization tree in time and/or frequency to organize sub-bandsub-channels into allowable combinations for sub-band channels; using adiversity sub-channelization tree in time and/or frequency to organizediversity sub-channels into allowable combinations for diversitychannels.

In some embodiments, the method further comprises: using a bitmap orregion identifiers to indicate which of the allowable combinations ofsub-band basic access units are being used as sub-band channels, andwhich of the allowable combinations of diversity sub-channels are beingused as diversity channels.

In some embodiments, the method further comprises: for each sub-bandchannel or diversity sub-channel, sending a respective user identifier.

In some embodiments, the method further comprises performing partialtree activation by: using a respective sub-channelization tree toorganize sub-channels into allowable channels for at least one ofdiversity channel definition and sub-band channel definition; for atleast one sub-channelization tree activating a portion of thesub-channelization tree and sending information identifying the portion;assigning channels from the portion of the sub-channelization tree.

In some embodiments, activating a portion of the sub-channelization treecomprises activating a certain set of consecutive levels within thetree.

In some embodiments, activating a portion of the sub-channelization treecomprises activating a respective set of consecutive levels within thetree for each of a respective set of at least one defined top node.

In some embodiments, the set of consecutive levels are defined by arespective top level and a respective bottom level for each top node.

In some embodiments, the set of consecutive levels are defined by thetop node and a respective bottom level for the top node.

In some embodiments, activating a portion of the sub-channelization treecomprises: employing a first bitmap to identify a subset of nodes of thesub-channelization tree that are active.

In some embodiments, the method further comprises: using a second bitmapto identify which nodes of the subset of nodes are being assigned, andfor each node being assigned, assigning a user identifier.

In some embodiments, the method further comprises: updating the partialtree activation from time to time.

In some embodiments, updating the partial tree activation from time totime comprises: sending update information only for segments of the treethat have changed.

In some embodiments, the method comprises, for each segment to bechanged: sending an indication of the segment that is to be changed;sending updated activation information for the segment.

In some embodiments, the method further comprises: dynamically poweringoff a partial resource of bandwidth.

In some embodiments, the method further comprises: dynamically poweringoff a partial resource of bandwidth.

In some embodiments, the method further comprises sending informationidentifying which resources have been powered off.

In some embodiments, sending information identifying which resourceshave been powered off comprises one of: sending a two dimensional bitmap indicating which resource blocks are powered off; sending a onedimensional bit map indicating which sub-bands are powered off; sendinga one dimensional bit map indicating which sub-bands are powered off atsome point in the slot, and sending additional information indicatingwhen they are powered off within the slot.

In some embodiments, the method further comprises: scheduling eachreceiver to either a sub-band channel or a diversity channel as afunction of information received from receivers.

In some embodiments, the method further comprises: defining a priorityfor each receiver; attempting to schedule each receiver in order ofpriority.

In some embodiments, attempting to schedule each receiver in order ofpriority comprises: if the receiver is a sub-band channel receiver,attempting to assign a sub-band channel to the receiver; if the receiveris a diversity channel receiver, attempting to assign a diversitychannel to the receiver.

In some embodiments, attempting to assign a sub-band channel to thereceiver comprises: receiving a selection of one or selected sub-bandsthe receiver has chosen; if the selected sub-band are available,determining if scheduling the receiver using the selected sub-bands willimpact already scheduled diversity users and if not scheduling thereceiver using the available selected sub-bands; if the selectedsub-band are available and scheduling the receiver using the selectedsub-bands will impact already scheduled diversity users, attempting tore-schedule at least one impacted diversity user and if successful inre-scheduling the receiver using the available selected sub-bands.

In some embodiments, the method further comprises: allocating someresources persistently over multiple slots and allocating otherresources non-persistently.

In some embodiments, the method further comprises: allocating someresources persistently at the beginning of each slot, and signalinginformation indicating how much resource has been allocatedpersistently, with non-persistent allocations following the persistentallocations.

In some embodiments, the method further comprises using asynchronousHARQ for retransmission, and assigning all retransmitted packets ahigher priority than non-retransmitted packets.

In some embodiments, a method further comprises: for a given schedulingperiod, allocating sub-band channels up to an allocation threshold.

In some embodiments, for a given scheduling period, allocating sub-bandchannels up to an allocation threshold comprises: allocating sub-bandchannels first up to the allocation threshold; defining diversitychannels using sub-carriers left over after sub-band channel assignment.

In some embodiments, for a given scheduling period, allocating sub-bandchannels up to an allocation threshold comprises: allocating sub-bandchannels up to the allocation threshold; defining diversity sub-channelsusing all OFDM sub-carriers, and allocating diversity sub-channels todiversity channels; transmitting each diversity channel punctured insub-carrier locations that are common between the diversity channel andan assigned sub-band channel.

In some embodiments, the method further comprises: persistentlyallocating a sub-band or diversity channel transmission resource forVoIP traffic.

In some embodiments, the method further comprises: using one of two MCS(modulation and coding scheme) levels VoIP traffic by assigning one ofthe two MCS levels at a beginning of a call and only changing the MCSlevel if a significant change in a receiver's average reported CQI isdetected.

In some embodiments, the method further comprises: if a mobile stationreports a CQI that maps to a higher MCS than an operating MCS,decreasing a transmit power by an amount specified for the differencebetween the two MCS levels; and if the mobile station reports a CQI thatmaps to a lower MCS than the operating MCS then performing no poweradjustment.

According to another broad aspect, the invention provides a methodcomprising: receiving OFDM symbols using a plurality of sub-carrierswithin an OFDM band; the OFDM symbols collectively containing diversitychannels and sub-band channels, each diversity channel utilizing aplurality of sub-carriers distributed across the OFDM band, and eachsub-band channel utilizing a contiguous set of sub-carriers within theOFDM band; at least some of the OFDM symbols simultaneously includingsub-carriers utilized by a sub-band channel and sub-carriers utilized bya diversity channel; receiving signaling information indicating whichdiversity channel or sub-band channel to extract.

In some embodiments, the method further comprises: receiving signalinginformation allowing a determination of how diversity channels andsub-band channels are defined.

In some embodiments, the signaling information comprises anidentification of which sub-carriers are occupied by sub-band channels,the diversity channels being systematically defined using left oversub-carriers.

In some embodiments, a receiver is adapted to implement the method assummarized above.

In some embodiments, a transmitter is adapted to implement the method assummarized above.

According to another broad aspect, the invention provides a transmittercomprising: an OFDM modulator that produces OFDM symbols fortransmission from a plurality of inputs; a channelizer that maps symbolsto inputs of the OFDM modulator such that the OFDM symbols collectivelycontain diversity channels and sub-band channels, each diversity channelutilizing a plurality of sub-carriers distributed across an OFDM band,and each sub-band channel utilizing a contiguous set of sub-carrierswithin the OFDM band, such that at least some of the OFDM symbolssimultaneously including sub-carriers utilized by a sub-band channel andsub-carriers utilized by a diversity channel.

According to another broad aspect, the invention provides a systemcomprising: at least one transmitter and at least one receiver; the atleast one transmitter and the at least one receiver communicating usingOFDM symbols that collectively contain diversity channels and sub-bandchannels, each diversity channel utilizing a plurality of sub-carriersdistributed across an OFDM band, and each sub-band channel utilizing acontiguous set of sub-carriers within the OFDM band, such that at leastsome of the OFDM symbols simultaneously including sub-carriers utilizedby a sub-band channel and sub-carriers utilized by a diversity channel.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described withreference to the attached drawings in which:

FIGS. 1A and 1B are diagrams of OFDM symbol structures that allow forthe co-existence of both sub-band channels and diversity channels;

FIG. 2 is a diagram of an OFDM frame structure in which OFDMsub-carriers are divided into sub-bands, with each sub-band beingassigned to one of sub-band channel use of diversity channel use;

FIG. 3 is a diagram of a frame structure in which the sub-carriersallocated for diversity channel use of FIG. 2 are further broken downinto three different diversity channels;

FIG. 4 is another diagram of an OFDM frame structure showing theassignment of both diversity channels and sub-band channels with pilotsinserted in the first OFDM symbol in each group of seven OFDM symbols;

FIG. 5 is a diagram of a frame structure again showing the co-existenceof sub-band channels and diversity channels, in this case also includinga scattered pilot and a control channel;

FIG. 6 is a table showing example parameters for sub-band definition;

FIGS. 7 and 8 shown are diagrams of example frame structures in whichthe OFDM sub-carriers are divided into sub-bands, and the OFDM symbolsof a given slot are divided into sub-slots;

FIGS. 9A and 9B are diagrams of two different approaches tosub-channelization using sub-channelization trees;

FIG. 10 is a diagram showing how sub-carrier definitions assigned to agiven sub-channel can hop over time;

FIG. 11 is a diagram of an example of sub-channelization tree nodenaming;

FIG. 12 is a diagram of an example of diversity sub-channel definitionthat takes place using sub-carriers leftover sub-band channelassignment;

FIG. 13 is a diagram of another example of diversity sub-channeldefinition that uses sub-carriers leftover after sub-band assignment;

FIG. 14 is a diagram of another example of diversity sub-channeldefinition using sub-carriers leftover after sub-band channelassignment;

FIG. 15 is diagram of another example of diversity sub-channeldefinition using sub-carriers leftover after sub-band channelassignment;

FIG. 16 is diagram of another example of diversity sub-channeldefinition using sub-carriers leftover after sub-band channelassignment;

FIG. 17 is another example of diversity sub-channel definition;

FIG. 18 is an example of a diversity sub-channelization tree using thedefinition of FIG. 17;

FIG. 19 is a diagram of an example of the assignment of resource blocksto sub-band channels;

FIG. 21 is a diagram of an example of resource block assignment forsub-band channels with two examples of naming approaches that can beused;

FIG. 22 is a diagram showing another naming approach for naming sub-bandchannels;

FIGS. 23A and 23B are further examples of sub-band channel definitionand naming;

FIGS. 24 through 26 are diagrams of three different examples ofdiversity sub-channelization in which all of the sub-carriers areemployed for diversity sub-channelization notwithstanding whether or notsub-band channels have been assigned;

FIGS. 27 to 32 are diagrams showing how a reduced portion of an overalltree can be employed to reduce the amount of signaling required, and howupdates to such a tree can be achieved;

FIG. 33 is a diagram of an example of temporarily switching offsub-bands within the overall OFDM resource;

FIG. 34 is a diagram of a set of OFDM transmissions that do not allowfor the co-existence of sub-band channels and diversity channels onsingle OFDM symbols;

FIG. 35 is a block diagram of a cellular communication system;

FIG. 36 is a block diagram of an example base station that might be usedto implement some embodiments of the present invention;

FIG. 37 is a block diagram of an example wireless terminal that might beused to implement some embodiments of the present invention;

FIG. 38 is a block diagram of a logical breakdown of an example OFDMtransmitter architecture that might be used to implement someembodiments of the present invention;

FIG. 39 is a block diagram of a logical breakdown of an example OFDMreceiver architecture that might be used to implement some embodimentsof the present invention;

FIG. 40 is a flowchart of an example method of scheduling diversityusers and sub-band users.

DETAILED DESCRIPTION

A broad aspect of the invention provides an OFDM channelization systemand method in which sub-band channels and diversity channels aretransmitted simultaneously within the same OFDM symbol. Each sub-bandchannel employs a contiguous set of sub-carriers. Each diversity channelincludes a set of sub-carriers that are not entirely contiguous, andthat are diversity throughout across a frequency band. The conventionalmeaning of non-contiguous applies here, namely that there are at leastsome gaps between some of the sub-carriers.

FIG. 1A shows the co-existence of two types of channels in accordancewith an embodiment of the invention. In this example, some of thesub-carriers, collectively indicated at 20, are dedicated for diversitychannels, while some of the sub-carriers, collectively indicated at 22,are dedicated for sub-band channels. It can be seen that during anygiven OFDM symbol interval, for example OFDM symbol 24, diversitychannels and sub-band channels are simultaneously supported. In theparticular example illustrated, the OFDM sub-carrier set is divided intosub-bands each containing a fixed number of sub-carriers, and theoverall OFDM resource in time and frequency is divided into resourceblocks, each resource block consisting of one sub-band in frequency overa fixed number (one or more) of OFDM symbol intervals. When a resourceblock is allocated for sub-band channel use, all of the sub-carriers ofthe resource block are allocated to the same sub-band channel. In someimplementations, a given sub-band channel is only allowed to occupy asingle sub-band; in other implementations a sub-band channel can occupya maximum of two adjacent sub-bands; in other implementations, a givensub-band channel is allowed to occupy an arbitrary number of multipleadjacent sub-bands. Many examples of sub-band channel definitions areprovided below. When a resource block is allocated for distributedchannel use, multiple distributed channels may use the resource blockand other resource blocks, or a single distributed channel might use theentire resource block together with other non-adjacent resource blocks.Many examples of distributed channel definitions are provided below. Insome embodiments, the size of the resource block is selected as afunction of the coherence bandwidth such that for sub-band channels theentire set of sub-carriers experiences a similar channel. Once theoverall band of sub-carriers has been assigned to resource blocks, eachresource block is then used in its entirety either in the constructionof diversity or sub-band channels. In the example of FIG. 1A, thisassignment does not change from one OFDM symbol duration (in the timedirection) to another. In another embodiment, illustrated by way ofexample in FIG. 1B, the assignment of resource blocks to diversitychannels or sub-band channels can change over time. In FIG. 1B, it canbe seen that during OFDM symbol interval 26, there are four resourceblocks that are used for diversity channels, and three resource blocksthat are used for sub-band channels whereas during OFDM symbol interval28, there are four resource blocks being used for sub-band channels andthree resource blocks being used for diversity channels. Furthermore itcan be seen that the assignment of the resource blocks changes on a perOFDM symbol basis. FIG. 1A has been used to show a specific example ofresource block assignment that is statistically defined in time. Thenumber and allocation of fixed in time resource blocks is animplementation specific parameter. Similarly, for the example of FIG.1B, a very specific layout of resource blocks for diversity channels insub-band channels that changes over time has been shown, for examplethrough dynamic assignment. More generally, any appropriate layout ofresource blocks for these two channel types can be employed.

Another example of the co-existence of the two types of channels willnow be described with reference to FIG. 2. In this example, OFDM symbolsare divided into TTIs (transmit time interval). In the illustratedexample, each TTI consists of seven consecutive OFDM symbols, but ofcourse an arbitrary number of symbols could be employed. One such TTI isindicated at 30. The first symbol in each TTI, namely symbol 32 for thefirst TTI 30, is used as a reference symbol. This might for exampleinclude pilot and control information. More generally, each TTI has atleast one reference symbol. The remaining six OFDM symbols 34 are usedfor traffic channels. In the frequency direction, the availablebandwidth of sub-carriers is divided into resource blocks. In aparticular example, each resource block might contain 25 sub-carriers.Then, each resource block is assigned to be used for either sub-bandchannels or diversity channels. In the illustrated example, resourceblocks 36 are being used for sub-band channels while resource blocks 38are being used for diversity channels. With this particular example, theassignment of resource blocks to sub-band channels and diversitychannels is fixed, but in another implementation this can be allowed tochange as was the case for the example of FIG. 1B. With the example ofFIG. 2, the reference symbols are inserted in a TDM (time divisionmultiplexed) fashion, with every seventh symbol being a reference symbolbut different frequencies can be employed.

Having allocated the sub-carriers and OFDM symbol durations to eithersub-band or diversity mode, there are many ways to define diversitysub-channels using the allocated sub-carriers. A first example will nowbe described with reference to FIG. 3 where the reference symbolinsertion, TTI size, and resource block assignment is assumed to be thesame as was described with reference to FIG. 2. In this case, threedifferent diversity channels are defined using the assigned resources.The resources assigned for the first channel are indicated at 46. Thisconsists of a single resource block during the first two OFDM symbols 40reach TTI, a single resource block during the next two OFDM symbols 42reach TTI, and a single resource block 50 during the next two OFDMsymbols 44 reach TTI. The location in frequency of the three resourceblocks that make up the diversity channel is different and that is whythe channel is to be considered a diversity channel. A similarassignment of resource blocks is shown for channels 48 and 50. In theillustrated example, the channel assignment is constant from one TTI tothe next, but this need not necessarily be the case. It should bereadily understood that using the model of FIG. 33, an arbitrary numberof diversity channels could be created assuming sufficient resources areassigned for diversity channel use. Furthermore, as was the case withthe example of FIG. 2, the number of OFDM symbols in each TTI and thenumber of sub-carriers in each resource block is to be considered animplementation specific detail.

Referring now to FIG. 4, shown is another example of the co-existence ofsub-band and diversity channels. With this example, the availablesub-carriers are again divided into resource blocks. In the illustratedexample each resource block is eight sub-carriers, but other numbers canbe employed. The first OFDM symbol 60 of each TTI is used as a referencesymbol and in the particular example illustrated the reference symbol isused for pilot symbol insertion. In the illustrated example, MIMOtransmission is assumed with four transmit antennas. The pilots areinserted with a respective distributed set of sub-carriers assigned tofunction as the pilot for each antenna. In the particular exampleillustrated, the first sub-carrier and every fourth sub-carrierthereafter is used for a first antenna; the second sub-carrier and everyfourth sub-carrier thereafter is used for a second antenna and so on. Infrequencies that one antenna is transmitting a pilot, the other antennastransmit nulls. Until the next symbol containing pilot information, theOFDM symbols 62 are used for data transmission. As was in the case inprevious examples, several of the resource blocks 64 are allocated forsub-band channels while several of the resource blocks 66 are allocatedfor diversity channels. In this example, the sub-carriers are allocatedfor diversity channels are used to implement three different diversitychannels indicated at 68, 70, 72. In this example, the first two OFDMsymbols 74 are used for the first diversity sub-channel; the next twoOFDM symbols 76 are used for the second diversity sub-channel 70, andthe third pair of OFDM symbols 78 is used for the third diversitychannel 72. The channels are still diversity channels in the sense thatthey employ sub-carriers from resource blocks 66 that are spreadthroughout the spectrum. In contrast, for the sub-band channels one ormore resource blocks would be allocated to a given user. The frequencybreakdown between sub-band and diversity channels may be the same in themultiple antenna case. However, more generally, the breakdown betweensub-band channels and diversity channels need not be the same for themultiple transmit antenna case and can be defined on a per antennabasis. A specific example has been shown in FIG. 4 that is suitable fora four transmit antenna system. Of course appropriate modificationscould be made to support systems with fewer or greater numbers ofantennas. Furthermore, the particular layout of sub-band resource blocksand diversity resource blocks is only an example. Similarly, the size ofthe TTI 62, and the number of sub-carriers in each resource block arealso implementation specific details.

For the OFDM symbol used for pilot insertion in FIG. 4, for a given OFDMsub-carrier, only a single antenna transmits a pilot. In this manner,there is no interference between the pilots from the various antennas.Thus, the pilots are scattered with the FIG. 4 embodiment with a spacingof four sub-carriers between the pilots for a given antenna, and aspacing of every seven OFDM symbols. More generally, a scattered pilotdesign is one that includes pilots for each antenna that are spaced infrequency and time. FIG. 5 shows another example of a scattered pilotdesign in which pilots for each antenna are inserted in a diamond shapedlattice with pilots for antennas 1, 2, 3 and 4 indicated at 90, 92, 94,96 respectively. The structure of the channels in FIG. 5 consists of areference OFDM symbol 98 that is used to as a control channel, followedby six OFDM symbols 100 used for traffic. The control channel is used totransmit the same content from all of the antennas for this example. Theparticular breakdown of the OFDM symbols 100 for traffic is the same aswas the case for the FIG. 4 example, with sub-band channels indicated at102 and three diversity channels indicated at 104, 106, 108. However, inthis case the diamond shaped lattice pilot pattern has been puncturedacross both the control channel 98 and the data channels 100. A firstoption for puncturing is that it is a pure puncture with actual contentfrom the respective data channels simply being omitted. In this case, itwould be necessary that the forward error correction coding or othererror correction techniques be employed to enable the recovery of themissing contents. Another option is that the payload size is changed forchannels that have punctured locations. For example, for the firstsub-band channel 102, it can be seen that in the absence of the pilotinsertion there would be 8 sub-carriers by 6 OFDM symbols=48 datalocations. When the puncturing has been performed, six of these areremoved and as such there is now room for 42 data locations. If thepayload is proportionately reduced in size, then forward errorcorrection does not need to be relied upon to recover any missinginformation, at least not any missing information due to punctured pilotchannels. In FIG. 5, a very specific example has been shown. It is to beunderstood that the number of OFDM symbols used for data in each slot isan implementation specific detail; the number of OFDM sub-carriers ineach resource block is implementation specific; the particular layout ofthe scattered pilots is implementation specific; the number of antennasemployed is implementation specific; the arrangement and layout of thesub-band channels versus the diversity channels is implementationspecific.

FIG. 6 is a table showing various examples of how specified systembandwidths can be used to implement OFDM channelization structures.

In another generalized approach to channelization, a scheduling periodis referred to as a “slot”, this consisting of a set of L (L≧1) OFDMsymbols.

All the sub-carriers within a slot (time domain) and whole band(frequency domain) are viewed as a sub-carrier pool. A slot in the timedomain is divided into M sub-slots with each sub-slot including one ormultiple consecutive OFDM symbols or symbol pairs. The whole band(frequency domain) is divided into N sub-bands with each sub-bandincluding multiple contiguous sub-carriers. Thus the sub-carrier pool iseffectively divided into an M×N resource block space with each resourceblock including one or multiple sub-slots and multiple contiguoussub-carriers. The sub-slot duration in time is equivalent to theresource block duration in time. M and N can be updated dynamically onslot basis or statically on a few slots basis based on trafficstatistics. M is ≧1, and N≧2.

It is readily apparent how the examples presented thus far can fit inwith this generalization, allowing for the insertion of additional OFDMsymbols for reference, pilot or control. Two specific examples ofresource block definition are given in FIG. 7. A first example,generally indicated at 120 involves a sub-carrier space with 48sub-carriers, and a slot length consisting of eight OFDM symbols. Thetime domain slot is divided into M=2 sub-slots each contains four OFDMsymbols, and the frequency domain is divided into N=4 sub-bands eachcontaining 12 contiguous sub-carriers. The result is a 4.times.2resource block space. A second example, generally indicated at 122,involves the same set of 48 OFDM sub-carriers and the same eight OFDMsymbols per slot. In this case, the entire eight OFDM symbols are usedto define a single sub-slot, and the 48 OFDM sub-carriers are divided inthe frequency domain into eight sub-bands each containing six OFDMsub-carriers. Thus in this example, there is an N=8 by M=1 resourceblock space.

Referring to FIG. 8, another example of resource block definition isshown in which 48 sub-carriers over eight OFDM symbols are divided intoN=8 sub-bands each with six OFDM sub-carriers, and two sub-slots eachcontaining four OFDM symbols for an 8×2 resource block space.

Having defined the N×M resource block space, each of the resource blocksis then used for sub-band or distributed channels.

A slot can be configured to include the two types of channels, namelysub-band channel and diversity channel. A sub-band channel includes acontiguous set of one or more resource blocks. A diversity channelincludes multiple sub-carriers with those sub-carriers distributedacross multiple resource blocks. Many examples of how the divisionbetween sub-band channels and diversity channels can be implementedwithin a slot will be described below. In some of these, sub-bandchannel resources are allocated first, and then all leftover resourcespace within a slot is available for diversity channels.

Referring again to FIG. 8, in the illustrated example, a single resourceblock has been assigned to create a first sub-band channel 130; tworesource blocks that are consecutive in time have been assigned to asecond sub-band channel 132, and two resource blocks that are adjacentin frequency have been assigned for a third sub-band channel 133. Theremaining capacity is then available for diversity channels.

Diversity Channel Definition Using Diversity Sub-Channelization

In some embodiments, the resource blocks left over after sub-bandchannel assignment are used to define a set of diversity sub-channels,and then each diversity channel is defined to include one or multiplediversity sub-channels. Various options for diversity sub-channelizationexists, and several examples will be described below. In someembodiments, the diversity sub-channels are systematically defined suchthat given a set of available sub-carriers, the same set of diversitysub-channels will always result. With this approach, assuming atransmitter and a receiver both know the systematic definitions that arebeing applied, given a set of sub-carriers available for diversitysub-channelization, both the transmitter and receiver will know thesub-channel structure. The sub-channelization tree approaches describedbelow are examples of this systematic sub-channel definition approach.

In a first example, sub-band-wise sub-channelization is performed. Adiversity sub-channel is defined by taking at least one selectedsub-carrier within a sub-band into consideration. The definition is thenapplied to all available resource blocks for diversity channels. Inother words, the diversity sub-channel includes a correspondingsub-carrier in the same position within each sub-band available fordiversity channelization. For example, a diversity sub-channel mightconsist of the first sub-carrier of each sub-band available fordiversity channelization.

In another option, leftover space wise sub-channelization is performed.Diversity sub-channels are defined by taking all leftover sub-carriers(after sub-band allocation) in one or more OFDM symbols into theconsideration.

In some embodiments, a diversity sub-channel includes the samedefinition is applied across however many OFDM symbols are to beincluded in a resource block. In other embodiments, a diversitysub-channel definition changes from one OFDM symbol to the next within aresource block, for example through frequency hopping. An example ofthis is given below.

With diversity sub-channels thus defined, a diversity channel isconstructed from one or more such sub-channels.

In some embodiments, where channel definitions are not fixed, signalingis employed to let each mobile station know where within the overallavailable resource their particular content is located. In one exampleof such signaling a two-dimensional bitmap is employed to indicate wherethe sub-band channels are versus where the diversity channels are. Thefollowing is an example of such a two-dimensional bitmap for theresource allocation shown in FIG. 8, where:

-   -   N=8, M=2:    -   [1 0 1 0 0 0 0 0    -   0 0 1 0 0 1 1 0]

Each “1” in the two-dimensional bitmap represents a resource block thatis being allocated for sub-band channel use. It can be seen how the “1”sin the bitmap above correspond with the sub-band channels 130, 132, 133shown in FIG. 8. Then, for each one bit in the two-dimensional bitmap, auser ID is signaled. For example, user IDs 1, 2 and 3 might be signaledfor the five “1” bits that appear in the bitmap as follows:

-   -   {User ID=1    -   User ID=2    -   User ID=2    -   User ID=3    -   User ID=3}.

In another option for resource allocation signaling, a one-dimensionalbitmap can be employed, with a single bit indicating for each sub-bandwhether or not sub-band channels are to be included in that sub-band.The following is an example of such a one-dimensional bitmap for theallocation of FIG. 8:

-   -   N=8 [1 0 1 0 0 1 1 0]        This indicates that the first, third, sixth and seventh        sub-bands are for sub-band channel user, but does not indicate        the particular channel assigned to each sub-band thus reserved.        To achieve this, for each “one” bit in the one-dimensional        bitmap, information is sent that identifies the number of users,        and for each user, a start sub-slot index, and number of        sub-slots.

In yet another option for resource allocation signaling, each resourceblock is given a respective region ID. For the particular case of N=8sub-bands and M=2 sub-slots, there are a total of 16 resource blocks andfour bits can be used to identify region IDs. Then, for each region, thesignaling that is performed consists of the region ID and the user IDthat is to be transmitted in that region.

More generally, where channel definitions can change, any appropriatesignaling information can be sent that enables a determination of whichresource blocks are assigned to sub-band channels and which blocks areavailable to diversity channels. A user ID can also be sent for eachsub-band channel allocated.

In some embodiments, the diversity sub-channels are assigned using asub-channelization tree having multiple levels, with a first level inthe tree comprising a plurality of nodes each representing a singlesub-channel, and each subsequent level in the tree comprising one ormore nodes, each node in a subsequent level combining at least two nodesof a previous level and representing all sub-channels represented by theat least two nodes of the previous level. Specific examples are givenbelow. Each diversity channel can then be defined to include a set ofone or more sub-channels represented by a respective single node in thesub-channelization tree.

In order to signal diversity channel definitions, information can besent that associates each diversity channel with the respective singlenode in the sub-channelization tree. Specific examples below includebitmaps and region IDs.

Two examples of diversity channelization through sub-channelizationdefinition will be described with reference to FIGS. 9A and 9Brespectively. Both of these examples assume an input of a base set ofsub-carriers upon which sub-channelization is performed. Example methodsof defining the base set of sub-carriers are given below, suffice it tosay that the base set of sub-carriers may or may not be contiguous. Inthese examples, the diversity sub-channels are systematically defined bythe number K of sub-carriers to be used, and the number L ofsub-channels to be defined using those K sub-carriers. A first option isto employ a full diversity tree method to define the sub-channels. Witha full diversity tree method, a sub-channel includes non-contiguoussub-carriers if multiple sub-carriers are to be included in asub-channel. The diversity tree method allows sets of sub-channels to bedefined that contain increasingly large numbers of sub-carriers. Withthe example illustrated in FIG. 9A, generally indicated at 141, theassumption is that there are K=16 sub-carriers. At a first level in thediversity tree, generally indicated at 140, the K=16 sub-carriers areused to define L=16 sub-channels referred to as sub-ch[16,0] . . . ,sub-ch[16,15]. The next level in the diversity tree is generallyindicated at 142. Here, eight sub-channels are defined and labeledsub-ch[8,0], . . . , sub-ch[8,7]. Each of these sub-channels is shown toinclude two of the sub-channels from the first level 140 of the tree.Thus, in the second level 142, sub-ch[8,0] includes the 0.sup.th and8.sup.th sub-carriers. This process is repeated for subsequent levels inthe hierarchy. In the illustrated example, there are three more levels144, 146, 148. Each sub-channel in the third level 144 contains foursub-carriers, each sub-channel in the fourth level 146 includes eightsub-carriers, while the single node in the fifth level 148 includes allof the sub-carriers. It should be readily apparent how the examplepresented could be extended to cover an arbitrary number of sub-carriersK. With this sub-channelization definition, a given diversity channelcan be defined to include one or more of these sub-channels.

In a second example shown in FIG. 9B, generally indicated at 150, ahybrid diversity tree approach is employed. The first level in thediversity tree 152 is the same as the first level 140 of the firstexample 141. However, in generating the second level, pairs of adjacentsub-carriers from the first level are selected. Thus, in the secondlevel 154, sub-ch[8,0] includes the first two consecutive sub-carriers.After this, the sub-channels of the second level 154 are combined in asimilar manner to the first example, and third 156, fourth 158, andfifth 160 levels in the diversity tree can be defined. It is againreadily apparent how the approach given in the example 150 can beextended to cover an arbitrary number of sub-carriers. Furthermore,while in the illustrated example two consecutive sub-carriers have beencombined, in another embodiment it might be possible to include fourconsecutive sub-carriers, for example in the third level of thediversity tree 156. Contiguous groups of two, four or eight might beused to support STTD transmission formats for example. For applicationswhere the base set of sub-carriers are contiguous, the approach of FIG.9B allows for a better estimate of interference and channel conditionssince there are contiguous groups of sub-carriers.

In another example, diversity sub-channels include sub-carrier hoppingin the time domain based on a specific pattern that might for example bebase station specific. An example of this is shown in FIG. 10 where thesub-carrier selected for a given diversity sub-channel is indicated at162 for a first pair of OFDM symbols, 164 for a next pair of OFDMsymbols, 166 for a third pair of OFDM symbols and 168 for a fourth pairof OFDM symbols. The sub-carriers 162, 164, 166, 168 are all within asub-band. In this example, the sub-band has 16 sub-carriers but it isreadily apparent how this concept can be extended to an arbitrary numberof sub-carriers within a sub-band. In FIG. 10, the expression (+12)%16defines the sub-carrier hopping that occurs for this particular example.It means that after defining a first sub-carrier location (using thesub-channelization tree for example), the sub-carrier position for thenext OFDM symbol pair is determined by adding 12 to the current position(where the numbers 1 through 16 index into an arbitrarily defined baseset of sub-carriers that may or may not be contiguous) and performing amodulo 16 operation. With the example given, it can be seen that 16different sub-channels could be defined over four pairs of OFDM symbolswithin a sub-band. More generally, any appropriate mechanism ofsub-carrier hopping can be employed; of course the mechanism needs to bedeterministic in the sense that it can be reproduced at a receiver. Inthe above example, sub-carrier hopping occurs across OFDM symbol pairs;more generally, the hopping can occur at any defined time interval ofone or more OFDM symbols.

Having defined diversity sub-channels using one of the above-discussedapproaches, a diversity channel is defined to include one or multiplediversity sub-channel. Addressing schemes can be employed to identifydiversity channels. In one example, the addressing can be based on theposition in the sub-channelization tree. Referring back to the FIG. 9example, if a single diversity channel was to simply be one of thesub-channels referred to in the second level 142, then such a diversitychannel could be identified using any mechanism that allows theidentification of that position in the tree.

A specific example of diversity channel addressing will now be givenwith reference to FIG. 11. With this example, there are eightsub-carriers that have been used to create a four level diversity treewith eight nodes in the first level 172, four nodes in the second level174, two nodes in the third level 176, and one node in the fourth level178. A first option is to perform the addressing based on a bitmap. ForL=8 sub-channels in the first level, the size of such a bitmap would be15 because there are 15 nodes in the tree as a whole. As was the casewhere bitmaps were presented as an option for signaling the occupancy ofavailable sub-band channels, a bitmap can be transmitted to indicatewhich diversity sub-channels are occupied, together with user IDs forthe occupied sub-channels. This combination will completely specify thecontent of the diversity channels. In another example, each node in thetree is assigned a “region ID”. Since there are 15 nodes, four bits canused to uniquely identify each of the nodes in the tree. For example, inthe illustrated example region ID “0010” identifies one of the nodes inthe third level in the tree. It can be seen that a diversity channelhaving this region ID would include sub-carriers 8, 10, 12 and 14. Itshould be readily apparent how the bitmap or region ID approach could beapplied to any of the diversity sub-channel definitions presented thusfar.

In some embodiments, the sub-channel definition such as described aboveis applied across all of the sub-bands available to diversitytransmission, and during a given slot or sub-slot the same user isassigned such a combined capacity. An example of this will now be givenwith reference to FIG. 12 where in a given slot 180, containing twosub-slots 182,184 and containing eight sub-bands 186 through 200, threesub-band users have been assigned as indicated at 202, 204, 206. Theremaining sub-bands are used for diversity sub-channelization. In theillustrated example, each band contains eight sub-carriers and as such asub-channelization similar to that described with reference to FIG. 11can be employed as indicated generally at 208. Applying the samesub-channelization to all of the sub-slots and sub-bands that are notassigned for sub-band users, several diversity channels can be defined.Two particular diversity channels are illustrated by way of example withsub-carriers 210 being used to define a first diversity channel andsub-carriers 212 used to define a second diversity channel. In thiscase, the assignment is on a slot basis, with the sub-channelizationbeing applied for the entire slot and then assigned to a given diversitychannel. For consecutive OFDM symbol pairs, the sub-carriers assigned toeach sub-channel in this example alternate between two sets that areoffset from each other by one sub-carrier, this being an example of thehopping described by way of example above with reference to FIG. 10. Itcan be seen that there is still room for several additional diversitychannels. Then, the diversity channel can be identified simply by itsposition in the bitmap or region ID. For example, the diversity channel210 would simply be identified by position 4 in the bitmap, or region ID“0100”. Similarly, the diversity channel 212 would be identified byposition 6 in the bitmap, or region ID “0110”. The following is anexample of diversity channel assignment signaling that might be employedto that effect:

For bitmap case

-   -   Bitmap    -   For each 1 bit    -   {user ID}        For region ID case    -   Number of users    -   For number of users    -   {user ID    -   region ID}

The signaling might be employed as follows to signal the two diversitychannel shown in FIG. 12:

-   -   User ID=4, region ID=0100    -   User ID=5, region ID=0110

In another example, diversity channels are defined on a sub-slot basis.An example of this is shown in FIG. 13. This example includes asub-slot, sub-band structure the same as that of FIG. 12, and includesthe same three sub-band users 202, 204.206. Furthermore, the samediversity tree 208 is employed to define and identify sub-channels. Inthis case, three different diversity channels are illustrated. Thesub-carriers used for a first diversity channel are indicated at 220,for a second diversity channel at 222, and for a third diversity channelat 224. In this case, it can be seen that the content for the firstdiversity channel 220 spans both sub-slots 182, 184; the content for thesecond diversity channel 222 is located only in the first sub-slot 182,while the content for the third diversity channel 224 is located only inthe second sub-slot 184. Thus, a given diversity channel can be assignedto one or the other of the two sub-slots, or to both of the sub-slots.The following is an example of how diversity channel assignmentsignaling could be implemented to signal sub-slot contents for such animplementation:

For bitmap case

For each sub-slot

-   -   {Bitmap    -   For each 1 bit    -   {user ID}        For region ID case    -   For each sub-slot    -   {Number of users    -   For number of users    -   {user ID    -   region ID}

For the specific diversity channels shown in FIG. 13, the followingsignaling could be employed to completely identify the diversitychannels:

For diversity User

-   -   For sub-slot 0        -   User ID=4, region ID=0100        -   User ID=5, region ID=0110    -   For sub-slot 1        -   User ID=4, region ID=0100        -   User ID=6, region ID=1001

Note that in the examples of FIGS. 12 and 13, each sub-slot containedtwo OFDM symbol pairs, and sub-carrier hopping was employed for eachsub-channel. For example, it can be seen that the sub-channel identifiedby region ID 0100 (the sub-channel used by diversity channel 222) isoffset by two sub-carriers in the second OFDM symbol pair in sub-slot182. It should be readily apparent that sub-carrier hopping may or maynot be employed in a given implementation. Furthermore, it should alsobe readily apparent how the example of FIGS. 12 and 13 can be extendedto an arbitrary slot definition, an arbitrary sub-slot definition, anarbitrary number of sub-carriers and an arbitrary number of sub-bands.

The above examples are examples of sub-band-wise sub-channelization. Inanother implementation, diversity channelization is employed by creatinga diversity channelization tree taking into account all leftoversub-carriers after a sub-band channel assignment, this being so-calledleftover-space-wise-sub-channelization.

In a first example, such a diversity channelization is performed on aper sub-slot basis, and assignment to mobile stations is performed on aper-sub-slot basis. An example of this will now be given with referenceto FIG. 14 where a slot structure consisting of two sub-slots 230,232,and eight sub-bands 234 through 248 are defined each containing sixsub-carriers, and three sub-bands users are indicated at 250, 252, 254.During the first sub-slot 230, all of the available sub-carriers fordiversity channelization are combined at 256, and then thesesub-carriers can be used to create a sub-channelization tree such asdescribed previously. Then, diversity channels can be defined using thebitmap or region ID as in previous examples. In the illustrated example,during the first sub-slot, there are 36 sub-carriers available fordiversity channelization tree creation, while during the second sub-slot232, the sub-carriers available for diversity channelization areindicated at 258, and it can be seen that there are 30 suchsub-carriers.

In another implementation, all leftover sub-carriers in each sub-slotare combined as was the case in the FIG. 14 example, then, the two setsof sub-carriers are combined to create a single list of sub-carriers anddiversity sub-channelization is performed using the combined list.Referring to FIG. 15, an example of this is shown where the sub-carriers256 from the first sub-slot 230 and the sub-carriers 258 from the secondsub-slot 232 are combined to create a single list 258 which is then usedto create a diversity sub-channelization tree structure. In this case,assignment to mobile stations would be performed on a per slot basis. Inanother example of diversity channel definition, all leftoversub-carriers within a sub-slot and in a given sub-band are listed first.These sub-band based list are then combined into an overall list for theentire slot, and diversity sub-channelization tree is created using thiscombined list. Then, assignment to mobile stations is performed on a perslot basis. An example of this is given in FIG. 16 where again the samesub-slot and sub-band structure and sub-band user assignment is shown aswas the case for the FIG. 15 example. The available sub-carriers in thesecond sub-slot 232 are organized by sub-band as indicated at 260. Theseare then combined with similarly organized sub-bands of the firstsub-slot 230 to generate a combined list 262 that is then used for adiversity sub-channelization tree generation.

The above introduced slot diversity channel trees have been defined insuch a way that any sub-band channel assignments do not affect the slotdiversity channel tree structure and may be used to allocate resources.Presented below are further examples of slot diversity channel trees.For purposes of embodiments of the invention presented below the slotdiversity channel tree uses a diversity sub-channel which includes adefined number of L sub-carriers and each slot includes a defined numberM of OFDM symbols (or M sets of OFDM symbols of a defined size, forexample pairs). The slot structure may be provided by the following:

For a given OFDM symbol, the available sub-carriers are divided into Lgroups. Depending on the total number of suo-carriers N.sub.totavailable for diversity sub-channelization, the number of sub-channelsN.sub.ch will be N.sub.ch=N.sub.tot/(L) since there are L sub-carriersper sub-channel. For each OFDM symbol (or set of symbols) (m=1, . . . ,M) N.sub.ch sub-channels are defined by taking one sub-carrier from eachof the L groups. In a particular example illustrated in FIG. 17, M=10,and L=24. As such, a sub-channel [m=1, 2, . . . , 10, i=1, 2, . . . , N]is created by taking one sub-carrier from each group within OFDM symbol(or set of symbols) m. A diversity channel includes 24 sub-carriers. Thenumber N of sub-channels depends on the bandwidth available. For theseparticular numbers, N=3, 6, 12, 25, 39, 53 for bandwidths of 1.25 MHz,2.5 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz, respectively. In theillustrated example, the location of the sub-carrier within each groupthat is included in a given sub-channel is the same. Thus, for the firstsub-channel 272 illustrated in FIG. 17, this includes the firstsub-carrier of each of the 24 groups.

Sub-channelization is performed to define a set of base sub-channelssuch that the set includes a respective sub-set of sub-channels definedon each of a plurality of OFDM symbols (or sets of OFDM symbols). Thesub-channels can be defined as in the example of FIG. 17 by dividing theavailable sub-carriers into a number of groups equal to the number ofsub-channels to be defined, and taking a sub-carrier from each group,optionally in the same position. However, other methods of defining thesub-channels can be employed. The sub-channels thus defined (overmultiple OFDM symbols or sets of OFDM symbols) can then be combined intodiversity channels as in previous examples, for example using asub-channelization tree.

FIG. 18 shows an example of diversity sub-channelization that uses theset of base sub-channels as defined in FIG. 17. A hybrid diversity treemethod as generally described previously with reference to FIG. 9B isemployed, but more generally any method of combining the sub-channelsinto diversity channels can be employed. In the illustrated example,pairs of “adjacent” sub-channels are combined in the first level ofcombination (referred to as level 5 to 80) in FIG. 18. Note thatdepending upon the definition of the base set of sub-carriers, this mayor may not result in adjacent sub-carriers in the sub-channels definedin the first level of combination. The input to the sub-channelizationis similar to that described with reference to FIG. 17. Moreparticularly, all of the available sub-carriers for diversitysub-channelization are taken from all of the symbols (or groups ofsymbols) within the slot and a single diversity tree structure is madefrom those sub-carriers. In the illustrated example, a single slotconsists of 10 symbol pairs and there is a set of available sub-carriersfrom each symbol pair indicated at 288, 290, 292 for the first, secondand tenth symbol pairs respectively. The basic diversity sub-channel isindicated at 294 and includes one sub-carrier from each symbol pair.However, the next level combination at 286 combines diversitysub-channels in a manner such that there are pairs of consecutivesub-carriers. The remainder of the diversity tree is constructed asbefore with further levels indicated at 294, 296, 298, 300.

Referring now to FIGS. 19 through 23, a set of examples of sub-bandchannel definition will now be presented. Recall that with sub-bandchannels, a given sub-band user is allocated a set of resources that iscontiguous both in frequency and time within a given slot. Assuming thata resource block has N sub-carriers over M (≧1) OFDM symbols, resourcescan be assigned to a sub-band user by allocating them K×N sub-carriers(in other words K resource blocks where K≧1), over J sets of M OFDMsymbol intervals, where J≧1. The smallest unit of sub-band allocation isa single resource block. FIG. 19 shows a slot structure in which thetime domain runs from left to right along axis 302, and the frequencydomain runs from top to bottom along frequency domain axis 304. The slotstructure includes five OFDM symbol pairs (i.e. M=2) and eightsub-bands. There is a respective resource block 306 indicated in thetime-frequency plane for each possible sub-band over each set of symbolpair. For example, resource block 308 consists of the very firstsub-band of sub-carriers over the first pair of OFDM symbols. It isreadily apparent how such a breakdown could be prepared for an arbitrarynumber of sub-bands within an overall band, and for an arbitrary numberOFDM symbol pairs (or sets of M>=1 OFDM symbols) within a slot. Atime-domain tree structure, generally indicated at 310 allows for anefficient definition of any set of consecutive OFDM symbol pairs (orsets of M>=1 symbols). The first level on the tree has a resolutionequal to individual OFDM symbol pairs. In the illustrated example therewould be five nodes in this tree although these are not shown separatelyfrom the nodes for resource blocks. The next level in the tree containsnodes 312, 314, 316, 318 each of which uniquely identifies a pair ofconsecutive OFDM symbol pairs. For example, node 312 would identify thefirst and second OFDM symbol pairs. The third level in the tree hasnodes 320, 322, 324. Each of these nodes uniquely identifies threeconsecutive OFDM symbol pairs. For example, node 320 would identify theconsecutive combination of the first three OFDM symbol pairs. In thefourth level, nodes 326 and 328 each identify four consecutive OFDMsymbol pairs. For example, node 326 is associated with the first fourOFDM symbol pairs. Finally, in the fifth level of the tree, there is asingle node 320 that would be associated with all five OFDM symbol pairsof the slot. Thus, by uniquely identifying one of the nodes in the tree(there being 5+4+3+2+1=15 nodes) any consecutive set of OFDM symbolpairs can be uniquely identified. As was the case for earlier diversitydefinitions, the time-domain tree 310 can have associated bitmapping orregion identifiers to refer to particular nodes within the tree.

A similar tree structure is defined in the frequency domain to enablethe unique referencing of any allowable combination of contiguoussub-bands. In some implementations, a maximum of two contiguoussub-bands can be combined into a sub-band channel; in otherimplementations an arbitrary combination is allowed. In the illustratedexample, a complete tree (not shown) would have eight nodes in the firstlevel, seven nodes in the second level, etc., for a total of 36 nodes.The nodes can be identified again using a bitmap or region ID forexample.

In a particular example, an arbitrary node in the time-domain tree 310can be identified using four bits while an arbitrary node in thefrequency domain could be identified using six bits.

Having defined the time-domain tree 310, and the frequency domain tree,an arbitrary sub-band channel can be defined by combining a nodeidentified from the time-domain tree with a node identifier from thefrequency domain tree. For the purpose of example, a portion of thefrequency domain tree is illustrated. For example, a particular sub-bandchannel is indicated in FIG. 19 at 350, this containing three contiguoussub-bands over two consecutive OFDM symbol pair durations. This sub-bandcould be uniquely identified by the combination of the time-domain treenode identifier for node 314 and the frequency domain tree nodeidentifier for 360. This embodiment allows for sub-band resource to beallocated anywhere within the entire resource space.

In another embodiment, all sub-band channel resources are allocatedstarting from this first symbol pair (more generally the first symbol orgroup of M symbols). This allows for a simpler time-domain tree thatincurs less overhead. However, there is also less flexibility. Anexample of this is shown in FIG. 20 where the time-domain tree,generally indicated at 370, only includes nodes that represent thecombinations of consecutive OFDM symbol pairs starting from the start ofthe slot. Node 372 represents the first two OFDM symbol pairs, the nextnode 374 represents the first three OFDM symbol pairs, the next node 376represents the first four OFDM symbol pairs while the top node 378represents all five OFDM symbol pairs. The tree does not allow for areference to, for example, the third and fourth consecutive OFDM symbolpairs. It can be seen however that since there are only five nodes inthe tree (assuming the first node 371 is included) this can representedusing only three bits. The frequency domain tree structure could be thesame as that described with reference to FIG. 19.

Note that given implementations may limit the number of consecutivesub-bands that can be combined into a sub-band channel. For example, itmay be that only a maximum of two sub-bands can be combined into a givensub-band channel. In this case, the frequency domain tree would onlyhave two levels, the first level that uniquely identifies each sub-band,and the second level that uniquely identifies any pair of contiguoussub-bands. In this case, for the example of FIG. 19 where there areeight sub-band basics, there would be seven nodes in the next level ofthe tree for a total of 15 nodes in the frequency domain, and thesecould be uniquely identified using four bits.

Referring now to FIG. 21, shown is an example of how sub-band channelidentification might be performed for such an implementation, namely theimplementation of FIG. 19, but where only a maximum of two sub-bandbasic access units can be combined in a sub-band channel. Here, it canbe seen that in the time-domain tree 310 there are still a total of 15nodes, and these can be identified by a position in a bitmap (referredto as 1, 2, . . . , 15) or alternatively using a four bits node ID asshown. Similarly, in the frequency domain tree, generally indicated at380, this tree only including two levels as discussed above and having atotal of 15 nodes, each node can be identified either by a position inthe bitmap (1, 2, . . . , 15) or a four bit node identifier. Thus, atotal of eight bits can be used to identify any one of the permittedsub-band channels for the example of FIG. 21. Furthermore, the nodenaming conventions used in the frequency domain or time domain do notneed to be the same. For example, a bitmap approach could be used in thetime domain and a node ID in the frequency domain or vice versa. It isalso to be understood that any appropriate node naming convention couldbe employed. A particular sub-channel as indicated at 382, thisconsisting of two consecutive sub-bands over two OFDM symbol pairs. Thenode identifier might be the combination of the time domain nodeidentifier (1000) and the frequency domain identifier (1011) for aneight bit identifier consisting of 10001011.

In another embodiment of the invention, rather than labeling nodes inthe time domain and the frequency domain separately, each permutation ofa frequency domain node and a time domain node has a respective uniquelabel region ID. For the example of FIG. 21, there are 15 time domainnodes and 15 frequency domain nodes for a total of 225 nodes that areeach given a unique identifier. Thus, again eight bits could be used toidentify each of these 225 nodes uniquely. An example of this is shownin FIG. 22 which is the same tree structure of FIG. 21, but in whicheach node is uniquely labeled. In FIG. 22, only some of the nodesassociated with first sub-band are labeled, since the time-domain treeis shown extending from those nodes. However, for the case where everynode is to be given a unique label, a respective time domain tree suchas illustrated is constructed for each sub-band. Since there are 225nodes, these can be uniquely identified using 8 bit identifiers asshown.

In another example of channel definition and naming for sub-bandchannels, a two step approach is employed. In a first step, a bitmap isused to identify the resource blocks available for sub-band channeldefinition. For example, in a slot structure consisting of eightsub-band over four OFDM symbol pairs, the total resource would consistof 32 resource blocks, and as such a 32 bit two-dimensional bitmap couldbe used to identify for each resource block whether or not it is to beused for sub-band channel use. An example of such a two-dimensionalbitmap is indicated at 400 in FIG. 23A for a resource space that is4.times.8. The following is an example of the two-dimensional bitmap 400for the particular example of FIG. 23A:

[1 0 0 0 0 0 1 1

-   -   1 0 0 0 1 0 1 1    -   1 0 1 0 0 0 0 0    -   0 0 1 0 0 1 1 0]

FIG. 23B shows another example of sub-band allocation using thisapproach. In this case, the two-dimensional bitmap is indicated at 408.

The next step is to use a systematic naming method to name each sub-bandchannel that can be created using one or a combination of the resourceblocks identified for sub-band channel usage by the bitmap. By“systematic naming method” it is simply meant that the method can beconsistently applied to a given bitmap to give the same results. In theparticular example illustrated in FIG. 23A, a two step approach isperformed to the uniform naming. First, naming is performed in thefrequency domain with each individual sub-band being given a name, andwhere there is a set of contiguous sub-bands, a frequency domain tree isbuilt using those consecutive sub-bands. In the illustrated example thefirst naming step is indicated at 402, it can be seen that during thefirst OFDM symbol pair there are three sub-band identified in the bitmapas being available for sub-band channel usage, and these have beenidentified as 1, 2, 3 respectively. Furthermore, since sub-bands labeled2 and 3 are contiguous, a tree is built off that, and this results in anadditional node numbered 4. During the next OFDM symbol, there are foursub-bands available for sub-band channel usage and these have beenlabeled 5, 6, 7, and 8, and the combination of sub-bands labeled 7 and 8has been labeled 9. During the third OFDM symbol, there are only twosub-bands available for sub-band channel usage and these are labeled 10and 11. The fourth OFDM symbol pair, there are three sub-bands availablefor sub-band channel usage, and these are labeled 12, 13 and 14. Sincesub-bands labeled 13 and 14 are contiguous, there is an additional nodelabeled 15. Next, tree structures are built in the time domain whereappropriate as indicated at 404. This is again done systematically. Inthe illustrated example it is done starting at the top in the frequencydomain. Thus, since nodes 1, 5 and 10 are consecutive in time for agiven sub-band, any permutation of 1, 2 or 3 of these resource blocks isa valid sub-band channel definition. Thus, nodes 16 and 17 are used toidentify pairs of consecutive symbol pairs while node 18 is used toidentify all three of them in combination. Furthermore, node 19 has beenadded to indicate the combination of nodes 11 and 12; node 20 has beenadded to indicate the combination of nodes 2 and 7 and node 21 has beenadded to indicate the combination of nodes 3 and 8. Finally, node 22 hasbeen added to indicate the combination of nodes 4 and 6. Node 22 wouldrefer to the block of four resource blocks including nodes 2, 3, 7 and8.

Having completed such a naming convention, there are a total of 22 nodesand as such a 22-bit bitmap could be used or a five bit node ID could beused to assign any of these permutations of resource blocks for usagewith a given sub-band channel. The node ID or bitmap together with theoriginal two-dimensional bitmap 400 can be used to signal sub-bandchannel structure uniquely.

For the example of FIG. 23B, there are no contiguous sub-bands and assuch there is no tree structure in the frequency domain.

The following is an example of signaling that might be used to performchannel assignment in combination with the bitmap:

-   -   Number of assignments=00010    -   U1 (user identifier for a first user), node ID=01110, PHY        parameters    -   U2 (user identifier for a second user), node ID=10110, PHY        parameters

A particular naming convention has been described with reference toFIGS. 23A and 23B. More generally, after first signaling the resourceblocks to be used for sub-band channelization (for example using abitmap), any systematic naming convention can be applied to identifyeach permutation of contiguous sub-bands over consecutive sub-slots.

In the above described methods of allocating resources to sub-bandchannels or diversity channels, the assumption has been that sub-bandchannel resources are allocated first, and then what is left over isused to allocate to diversity channels. In another embodiment, asystematic approach to sub-band channel and diversity channel definitionis employed that does not make this distinction. Rather, the entire bandis made available for both sub-band channel use and diversity channeluse. However, priority is given to one channel type or the other wherethere is a conflict. In one embodiment, where a given sub-carrier isallocated for both a sub-band channel and a diversity channel, thecontents of the diversity channel are punctured or omitted, and thesub-carriers used for the sub-band channel contents. Receivers of thediversity channel can make use of signaling information to know whichsub-carriers of their diversity channel have been punctured by sub-bandchannel and as such will know which sub-carriers to ignore.

In a first embodiment, a sub-band channel definition approach is used inaccordance with any of the examples given above to allow a sub-bandchannel to be defined using a contiguous set of sub-carriers over one ormore OFDM symbols or symbol pairs. On top of this, a diversitysub-channel is using all of the sub-carriers within the band. Particulardiversity users are then assigned one or more of these diversitysub-channels. Where the diversity channels overlap with the assignedsub-band channels, the diversity channel contents are omitted in favorof the sub-band channel contents.

A specific example of this will now be described with reference to FIG.24 where a sub-band basic access unit slot structure is shown at 410 foran example slot that provides for a 4.times.4 resource block space, eachresource block consisting of eight sub-carriers by two OFDM symbols.Thus, each node in the tree 410 represents eight sub-carriers over twoOFDM symbols. The tree structure shown allows for any pair ofconsecutive basic access units to be combined in a sub-band channel. Insome embodiments, multiple groups of eight sub-carriers that are locatedcontiguously can also be combined in generating this sub-band channel aswas the case in previous examples. Thus, an arbitrary block of nodesfrom the tree 410 can be used to define a sub-band channel so long asthey are rectangular in shape. The entire set of 32 sub-carriers for thelast OFDM symbol pair in the tree 410 are shown generally indicated at412. These 32 sub-carriers are used to define basic access units fordiversity channel definition, i.e. diversity sub-channels. In theillustrated example, the 32 sub-carriers are arranged in groups of four,and every fourth sub-carrier is assigned to the same diversitysub-channel. A diversity sub-channelization tree is indicated generallyat 414. The lowest level diversity sub-channels are indicated at 417.One of these sub-channels 415 is shown to include the first sub-carrierfor each of the groups of four shown at 412. Four such diversitysub-channels are defined on the basis of the last OFDM symbol pair.Similarly, four diversity sub-channels are defined for the first, secondand third OFDM symbol pairs respectively for a total of 16 diversitysub-channels. It can be seen that each diversity sub-channel includeseight sub-carriers, the same as in the sub-band channel for thisexample. The diversity sub-channelization tree 414 can then be used todefine diversity channels that are combinations of diversitysub-channels. For example, node 419 in the tree would consist of thecombination of the first four diversity sub-channels, all of which areimplemented during the first symbol pair.

Referring now to FIG. 25, shown is an example of how the jointly definedsub-channels can be identified. In the particular example illustrated,each node in the basic access unit slot tree 410 for sub-band channelsand the basic access unit slot tree 414 for diversity sub-channelizationthat can be used in association with a user identifier to indicate thatthat user identifier is to use that channel, be it a sub-band channel ora diversity channel. In another possible implementation, a bitmapcontaining a respective bit for each of the sub-channels is transmittedwith a “1” in each position that is to be occupied. In addition to that,a user identifier can be transmitted in association with each “1” toidentify which user is to occupy that channel. In a particular exampleillustrated in FIG. 25, there are 40 nodes in the sub-band tree andthere are 31 nodes in the diversity tree 414 and as such a 71-bit bitmapcould be used to identify which sub-channels are occupied.

Referring now to FIG. 26, a specific example of sub-channel utilizationis shown where there are seven sub-band channels 416 occupied within thesub-band tree 410, and there are seven diversity channels 418 occupiedwithin the diversity tree 414.

With the examples of FIGS. 24 through 26, the assumption is that everysingle node in the sub-band tree or diversity tree is available for usein defining sub-band channels or diversity channels. In someimplementations, it may be advantageous to only activate certain nodeswithin the tree. For example, for conditions in which the smallestsub-channel will require a combination of at least two basic accessunits, it would not be useful to include the bottom nodes in thesub-band basic access unit tree because these would not ever be used ontheir own. By reducing the number of nodes in the tree, a particularchannel structure can be identified more efficiently. For example, if abitmap is used, a smaller bitmap can be sent to identify where theactive channels within the “active” channel set are. In general, theapproach is to signal which portion of the tree is active, and then toperform node naming for the active nodes, and to perform channelassignment using the nodes thus named. The partial tree activationapproach can be used with either the sub-band channelization tree,and/or the diversity sub-channelization tree or for the combination ofthe two.

In a first example, in order to activate a partial tree, entire levelsof the tree are de-activated or activated together by signaling the toplevel within the tree that is active and signaling the bottom levelwithin the tree that is active. An example of this is shown in FIG. 27,generally indicated at 420. Shown is a five level tree 422 within whichit is desired to activate only the nodes of levels three and four. Inother words, channels containing a single level five sub-channel are notto be allowed, and channels that correspond with level two (eightsub-channels) or level one (all of the sub-channels) are not allowed.This can achieved by signaling level three to be the top level and levelfour to be the bottom level which will then indicate that the activetree is that indicated generally at 424. At that point, node naming canbe employed using any of the examples described before to name each ofthe nodes within the active tree. In the particular example illustrated,there are only 12 nodes in the active tree, and as such a 12-bit bitmapcan be used or four bit region IDs can be used to identify individualnodes.

In another example, the approach is further refined to allow the top andbottom level to be defined for multiple segments within the tree, eachtree being defined by a respective top node. An example of this is alsoshown in FIG. 27, generally indicated at 430. Here, the same five leveltree 422 is shown, and there are two segments. The first segment 432 hasa top node 431, and the top level in the tree that is to be activatedbeneath that top node is the third level, and the bottom level to beactivated is the fourth level. Similarly, for the second segment 434having top node 435, the top level to be activated is level two, and thebottom level to be activated is level three. The resulting active treeis generally indicated at 436. Once again any appropriate namingapproach can be used to name the nodes thus identified. In theparticular example illustrated, there is a total of nine nodes and thusa 9-bit bitmap, or four bit region identifiers can be employed. Thefollowing is an example of a signaling scheme that could be used toindicate the active tree structure:

Number of Segments

For each segment

-   -   Top node    -   Top level of tree    -   Bottom level of tree        For Example 1 of FIG. 27:    -   Number of segments=1    -   top level=3, bottom level=4        For Example 2 of FIG. 27:    -   Number of segments=2    -   For segment 1 (top node ID=00001, top level=3, bottom level=4)    -   For segment 2 (top node ID=00010, top level=2, bottom level=3)

In accordance with an embodiment of the invention FIG. 28 presentsanother partial tree activation scheme which uses a bound tree approach.With this approach, rather than signaling a top node, and a top level ofthe tree and a bottom level of the tree for each of a plurality ofsegments, a top node is signaled for each segment, and a bottom levelfor each top node is signaled. Thus, all of the nodes beneath each topnode that is identified down to the associated bottom level are includedin the active tree. In the example of FIG. 28, a five level tree isindicated at 440, and two top nodes 441 are to be included in the activetree, and the bottom level is level four. Thus, the active tree thatresults is that shown generally indicated at 442. With such an activetree thus established, the node naming can proceed using any appropriatemethod for example some of the methods described previously.

In accordance with an embodiment of the invention FIG. 29 presentsanother partial tree activation scheme which uses a node activationapproach. With this approach, to begin all of the nodes that are activewithin an overall tree is identified. This can be done for example usinga bitmap. Once a smaller number of nodes is thus identified, theremaining active nodes are named using an appropriate naming approach.An example of this is shown in FIG. 29 where a five level tree is shownat 444 containing 31 nodes. A subset of these nodes are selected to beactive, these including the seven node shown in bold in FIG. 29. A31-bit bitmap can be transmitted to indicate that seven nodes that areactive. Then, as the active slot tree as generally indicated at 446, andeach of the active nodes can be named. In the illustrated example, sincethere are seven active nodes, three bits can be used to identify each ofthe nodes uniquely, or a 7-bit bitmap can be used to indicate which ofthe nodes in the active slot tree are used. In this case, it can be seenthat there is an unbalanced resource assignment since the nodes in theactive slot tree have differing amounts of resources assigned to them.

The nodes that make up the active tree can be updated either slowly ordynamically. In some embodiments, the entire tree can be updated. Inother embodiments, only the portions of the tree that have changed areupdated so as to reduce overhead. Two specific examples are illustratedin FIG. 30. In the first example, a top node is used to define theportion (or segment) of the tree that needs modification. Preferably thetop node is referred to using the full tree, i.e. prior to pruning thetree to be an active tree. In example 1 of FIG. 30, the active tree 450needs to be amended so as to be the active tree 452. Thus, the full treeidentifier for node 451 is identified, and then the new updateinformation for that node is provided. In this example, this consists ofa bottom level for the node, again referring to the full tree for thelevel definition. It is much more efficient to signal simply the singlenode 451 and its update information than to re-signal the entire activetree.

In example 2 of FIG. 30, the top node again is signaled, and then abitmap is used to indicate which sub-tended nodes are to be active afteramendment. Thus, having identified node 455, again with reference to thefull tree, a bitmap can be used to indicate which of the nodes are to beactive in the updated active tree 456. In the illustrated example, thisconsists of the three nodes 457.

Referring now to FIG. 31, two specific examples of assignment signalingwill be provided. For the bitmap approach, a bitmap is transmittedindicating which nodes in the active tree are assigned, and for eachnode, a respective user ID is signaled. The following is an example ofsuch a bitmap and user ID signaling for the active tree 460 of FIG. 31:

-   -   Bitmap:    -   100011111000    -   User IDs: U1, U2, U3, U4, U5, U6.

In another example, rather than using a bitmap, individual node IDs areassigned to individual user IDs. An example is shown in FIG. 31 wherethe number of nodes IDs being assigned is 2. An example of the signalingthat might be employed is as follows:

-   -   Number of assignments=0010 (2)    -   User ID U1 assigned to node ID=0000    -   User ID U2 assigned to node ID=0100

As in all of the other examples described herein, a physical layerparameters may also be transmitted in association with the assignmentsignaling if these are not known a priority to the receiver.

Three further signaling examples are will be described by way of examplewith reference to FIG. 32. In the first example, generally indicated at464, a 7-bit bitmap can be used to indicate which of the active nodesare being assigned, and then a user ID is transmitted for each bit inthe bitmap. For the illustrated example, the following signaling couldbe employed:

-   -   Bitmap 1110110    -   User IDs U1, U2, U3, U4, U5

For the second example generally indicated at 466, a node assignment canbe employed. The following signaling might be used:

-   -   Number of assignments=010 (2)    -   User ID U1 assigned to node ID 000;    -   User ID U2 assigned to node ID 001.

A third example is shown generally at 468 in FIG. 32. In this example,all seven active nodes are used and as such it is necessary to transmita bitmap to indicate which of the active nodes are being assigned.Rather, it is only necessary to signal a user identifier for each activenode.

Static Partitioning

Based on distribution of sub-band and diversity users and their trafficload, the partitioning could remain for a certain time and be updatedthrough a slow signaling. Any of the above approaches can be used forstatic partitioning.

Dynamic Partitioning

In some embodiments, for each slot, based on the scheduling algorithm,the partitioning between sub-band and diversity channels is dynamicallygenerated. The partitioning can be broadcast dynamically through atwo-dimensional bitmap. Any of the above approaches can be used fordynamic partitioning.

Examples have been described in which sub-band channels are allocatedfirst, and then diversity channels are generated using the remainingresource blocks. In some embodiments in which this sequence ofallocation is exercised, a threshold is defined that limits the amountof the total transmission resource that can be assigned to sub-bandusers. The reason for this is that if too much of the spectrum isoccupied by sub-band users, there may not be enough spectrum left todefine diversity channels that have an acceptable level of frequencydiversity as defined for a given application. In some implementations,once such a threshold is reached, no further sub-band channels areallowed to be scheduled. In other implementations, once such a thresholdis reached, no diversity channels are allowed to be scheduled, and theremaining bandwidth is made available for sub-band channel use.

Examples have also been described in which diversity channels aredefined using the entire set of OFDM sub-carriers, and in which sub-bandchannel allocation takes away from the sub-carriers of a given diversitysub-channel. Similar thresholding can be applied to ensure that thereare sufficient resources for the transmission of diversity channels. Insome embodiments, a threshold on the amount of sub-band channelbandwidth occupancy is defined.

Power Off of Partial Resource

In accordance with an embodiment of the invention, a scheme is providedfor supporting power off of a partial resource of bandwidth. Power offof partial resource (POPR) of bandwidth may be used in some cases inorder to control inter-cell interference and enhance cell coverage byallowing sub-carriers across a fractional slot to be turned offdynamically. The location and size of POPR in the slot may be cell (basestation) specific and may power off and on dynamically.

Various examples can be used to implement signaling that enables dynamicPOPR control. For cases where the POPR bandwidth is slowly updated, abitmap might be employed to identify the resources that are to bepowered off. For example, a one-dimensional (each bit corresponding to asub-band with the first bit for the first sub-band) or two-dimensionalbitmap (each bit corresponding to a resource block.

Referring now to FIG. 33, a one-dimensional bitmap can be used to signalthe POPR case generally indicated by 500 where it can be seen thatsub-bands 0 and sub-bands 6 are to be temporarily powered off. Aone-dimensional bitmap can be used to indicate that these sub-bands havebeen powered off. The following is an example of such a bitmap:

Example 1 One-Dimensional Bitmap (Frequency Domain)

-   -   [0 1 1 1 1 1 0 1], first bit corresponding to the first sub-band

In a second example, a two-dimensional bitmap is employed. This enablessub-bands to be turned off during specific time intervals within a slotstructure. An example of this is generally indicated at 502 in FIG. 33where a separate bit is used for each resource block. In this case, a32-bit bitmap could be employed. Alternatively, a one-dimensional bitmapfor frequency domain could be used first to indicate that sub-bands thatare affected together with additional information indicating how thesub-bands are affected. The following is an example of a frequencydomain bitmap for the example of 502 of FIG. 33:

Frequency Domain

-   -   [1 0 1 1 1 1 1 0]→sub-band 1 and 7 are affected

Having identified that sub-bands 1 and 7 are affected using theone-dimensional frequency domain bitmap, a one-dimensional bitmap forthe time domain for each of the affected frequency domain sub-bands canbe generated. The following is an example of this that indicates thatOFDM symbol pair (more generally OFDM symbol or group of M>=1 symbols) 2in the second sub-band is turned off and OFDM symbol 3 in the seventhsub-band is turned off:

Time Domain

-   -   For sub-band 1: [1 1 0 1]→OFDM symbol pair 2 is turned off    -   For sub-band 7: [1 1 1 0]→OFDM symbol pair 3 is turned off

When it comes time to define diversity channels, for example usingdiversity sub-channelization techniques described earlier, it will benecessary that both the transmitter and receiver would understand thatthe sub-carriers occupied by PCPR would not be available for diversitychannel construction. In this case, a reduced-size diversity channel canbe used to transmit a reduced amount of data; alternatively, the sameamount of data can be transmitted with the expectation that redundancyin the data can be leveraged at the receiver to compensate for themissing sub-carriers.

In another approach to providing for POPR locations, this can beachieved by simply by assigning the sub-band resources that are to beturned off to null users, for example with a MAC ID=0 in this manner,these channels will not be used. This provides for a very simple dynamicupdating of the resources to be turned off.

Scheduling

In accordance with embodiments of the invention scheduling schemes foran OFDM air interface which supports sub-band and/or diversity users arepresented below.

There are three cases that can be considered in scheduling the forwardlink resources:

-   -   All the users are sub-band users.    -   All the users are diversity users.    -   There is a mix of sub-band users and diversity users.

In some embodiments, a given mobile station can indicate its preferencefor sub-band channel or diversity channel assignment by indicatingwhether it would like to report a sub-band CIR or a full band CIR. Insome implementations, the system will give each mobile station what itwants. However, in other implementations although the mobile stationindicates whether it would like to report a sub-band CIR or a full bandCIR, the scheduler decides which of the users that indicate a preferencefor sub-band reporting actually report a sub-band CIR. For example, thescheduler can indicate to a mobile that would prefer to report one ormore sub-band CIRs to instead report a full band CIR, or vice versa,based on factors such as traffic type, buffer size, geometry or theratio of diversity users to sub-band users. More generally, schedulingeach user to be either a sub-band channel or a diversity channel can beperformed as a function of information received from users.

The first two cases (where all of the users are sub-band users or all ofthe users are diversity users) can easily be handled since the next userto be scheduled does not interfere with the previously scheduled users.However, the third case, where there is a mix of sub-band and diversityusers, is more complex. When a sub-band channel is scheduled it can takeaway sub-carriers from several diversity channels. If a diversity useris scheduled before a sub-band user, in the same slot, the number ofsub-carriers remaining in the diversity channel may not be sufficient totransmit at the assigned data rate.

The above three cases can be handled using the scheduling schemesdescribed below. In accordance with embodiments of the invention theschemes presented are in accordance with the channelization schemesdescribed above.

The broader concepts are not, however, limited in this regard and can beapplied to other channelization schemes including, for example, if thediversity channels take sub-carriers away from the sub-band channels orthe case where the sub-carriers used by the sub-band channels and thediversity channels are mutually exclusive.

With reference to FIG. 40, in accordance with an embodiment of theinvention a scheduling scheme is provided as follows:

40-1) Create a two-dimensional priority matrix, where the first N.sub.scolumns represent each user's priority for the individual bands and thelast column represents the priority for the entire band. If a mobile isnot reporting a CIR on each individual band then set the individualsub-band priorities for the user to zero. For mobiles that report a CIRfor some or all of the sub-bands, the diversity priority is set to zeroif the full band CIR is not reported. If both full band CIR and sub-bandCIR are reported and if the sub-band CIR maps to the same data rate asthe full band CIR then the sub-band priority may be set to zero as, inthis case, there may be no benefit to assigning a sub-band. Thefollowing is an example of such a matrix, where P.sub.i,j is thepriority for the i.sup.th user in the j.sup.th band, and P.sub.i is thei.sup.th user's priority for the entire band. Any appropriateprioritization scheme can be employed.

$\quad\begin{bmatrix}P_{1,1} & P_{1,2} & \ldots & P_{1,N_{b}} & P_{1} \\P_{2,1} & P_{2,2} & \ldots & P_{2,N_{b}} & P_{2} \\\vdots & \vdots & \ldots & \vdots & \vdots \\P_{n,1} & P_{n,2} & \ldots & P_{n,N_{b}} & P_{n}\end{bmatrix}$40-2) Create an available channel list that contains the basicsub-channels for both diversity and sub-band channels and the size ofeach unit on each transmit antenna. An example of such a channel list isas follows where D.sub.i is a diversity channel unit and S.sub.i is asub-band channel unit (the same as a resource block as definedpreviously). The same approach can be used for an arbitrary number (oneor more) of antennas by providing a column for each antenna.

Channel Available sub-carriers Available sub-carriers Unit on antenna 1on antenna 2 D₁ B_(D, 1) ⁽¹⁾ B_(D, 1) ⁽²⁾ D₂ B_(D, 2) ⁽¹⁾ B_(D, 2) ⁽²⁾ .. . . . . . . . D_(d) B_(D, d) ⁽¹⁾ B_(D, d) ⁽²⁾ S₁ B_(S, 1) ⁽¹⁾ B_(S, 1)⁽²⁾ . . . . . . . . . S_(s) B_(S, s) ⁽¹⁾ B_(S, s) ⁽²⁾40-3) Select the user with the highest priority from the two-dimensionalpriority matrix.40-4) Is the user a sub-band user?

If the user is a sub-band user (yes path, step 40-4) then at step 40-5,if there is an available sub-band channel on the chosen sub-band (yespath, step 40-8), and if the impact to the previously scheduleddiversity channels is below a threshold (yes path, step 40-9) (e.g. thenumber of sub-carriers that may be taken from the diversity channel andstill allow that diversity channel to be re-scheduled at an equivalentdata rate to what was assigned previously), or preferably there is noimpact, then a sub-band channel is assigned that has an impact to all ofthe diversity channels that is below a threshold at step 40-11. In someembodiments a sub-channel which has the least impact is assigned. If theimpact on diversity users is not below the threshold (no path, step40-9) then if the previously scheduled diversity channels cannot bere-assigned (no path, step 40-10) then a choice may be made not toschedule the sub-band user. Accordingly, the user's priority can be setto zero at step 40-14 and go back to step 40-3. Otherwise, continue. Ifthe impacted diversity channels can be re-assigned (yes path, step40-10) then the sub-band user is scheduled, and the diversity usersre-assigned at step 40-12.

After scheduling, the assigned sub-band channel is removed fromavailable channel list, and the size of diversity channels (availableand scheduled) is updated at step 40-13.

If the user is a diversity user (no path, step 40-4), then a diversitychannel is assigned to the user at step 40-6.

If there are available channels to assign and there are more users toschedule then go back to step 40-3.

A very specific method of scheduling has been described with referenceto FIG. 40. This is a very specific combination of features that ascheduler may employ. More generally, subsets of these features may bepresent in a given implementation.

For example, in some embodiments a scheduling method is provided thatinvolves scheduling each receiver to either a sub-band channel or adiversity channel as a function of information received from receivers.A selection of sub-bands, or sub-band CQI information, or a preferencefor sub-band vs. diversity channel are three examples of suchinformation.

In some embodiments, the method involves defining a priority for eachreceiver, and attempting to schedule each receiver in order of priority.

According to an embodiment of the invention, in the case of MIMOtransmission, using for example per antenna rate control (PARC) orspace-time transmit diversity (STTD), the scheduling procedure is thesame. However, for PARC or for the mixed case where some users are usingPARC and some STTD, the available channel list and the priority matrixmay be maintained per transmit antenna. Despite the fact that theexample shown above is for a MIMO scenario, the scheduling schemes setout above and below are applicable to a one antenna arrangement.

According to another embodiment of the invention, instead ofre-assigning the resources for the previously scheduled diversity usersafter a sub-band user is scheduled, the scheduler may account for theamount of resources that are required for each of the scheduleddiversity user and assign the actual diversity channels after the usersare selected and the sub-band users are assigned a sub-band channel.

When determining the impact of assigning a sub-band channel on thediversity channels, the number of sub-carriers remaining in thediversity channels and the distance between the sub-carriers may both beconsidered. The sub-band assignment should minimize the number ofsub-carriers taken away from the diversity channels and the distancebetween the remaining sub-carriers should be maximized.

According to another embodiment of the invention a multi-slot/persistentresource assignment scheme is provided by the following. In the case ofdelay sensitive traffic with a constant packet arrival rate, such asVoIP, the scheduler may pre-assign multiple slots spaced at an intervalequal to the packet arrival rate. The benefit of assigning multipleslots is that it reduces the signaling overhead. Since the VoIP usersare pre-scheduled, only the non-VoIP users are scheduled using the abovemethod.

The multi-slot assignment may start from the first OFDM symbol of theslot. If the multi-slot assignment does not completely occupy a symbolthen the remaining sub-carriers in the symbol belong to the same channelformat (diversity or sub-band). In a scheduling instance, the number ofchannel units that are used for multi-slot transmission are signaled bythe base station. That is to say the number of channel units issignaled, rather than the user, data rate and channel. This allows theother users to know how much was pre-assigned so they know where thecurrent assignment starts and it avoids the signaling associated withidentifying the user, data rate and channel, because it is the same asthe initial assignment. The non-persistent channel assignment may startfrom the first channel unit of the remaining channel units.

When a user is pre-scheduled for multiple slots, the data rate and theamount of resources may be kept constant. In order to track each user'schannel, power management may be used in place of rate control. If agiven user's channel improves, less power may be allocated to thesub-carriers assigned to the user and more power can be assigned to theusers that have a worse channel condition. Once a multiple slot formathas been assigned, subsequent sub-band allocation may be performed if itdoes not puncture any of the sub-carriers from the assigned multi-slotchannel.

In some embodiments, when the base station detects a silent slot from auser for a given number of slots, the base station removes thepersistent assignment until a non-silent slot is detected.

More generally, in some embodiments, scheduling is implemented so as toallocate some resources persistently over multiple slots and allocateother resources non-persistently. In some embodiments, the persistentlyallocated resources are located at the beginning of each slot andsignaling information is sent indicating how much resource has beenallocated persistently, with non-persistent allocations following thepersistent allocations.

VoIP traffic is a particular example of a type of traffic that wouldbenefit from persistent allocation in combination with synchronous HARQ.

In an embodiment of the invention providing persistently allocatedcapacity for VoIP with Synchronous HARQ, only two MCS (modulation andcoding scheme) levels are used for VoIP traffic. The MCS is assigned atthe beginning of the call and is only changed if transmitter (such as abase station) detects a significant change in the receiver's (such as amobile station) average reported CQI.

Since the MCS is constant for a number of transmissions while the mobilestation's CQI is varying, power management can be used to improve theuse of the resources. The mobile station reports CQI to the base stationfor this purpose; the CQI reporting can come in any form. Specificexamples include multi-level, differential, single bit up/down, two bitup/down/no change.

The power is adjusted based on the mobile station's reported CQI. Noadditional signaling from the base station to the mobile station isrequired. A mapping between the amount of power adjustment and thereported CQI is employed to select the power adjustment; this mapping isknown to both the base station and the mobile station.

In some embodiments, if the mobile station reports a CQI that maps to ahigher MCS than the operating MCS then the power is decreased by theamount specified for the difference between the two MCS levels. If themobile station reports a CQI that maps to a lower MCS than the operatingMCS then no power adjustment is performed.

According to another embodiment of the invention both persistent andnon-persistent transmissions may use asynchronous HARQ, where allretransmitted packets are assigned a higher priority thannon-retransmitted packets. In this case, a retransmission may bescheduled as soon as a NAK is received. The retransmitted packet may beassigned the same modulation and coding scheme as the initialtransmission, however, the assigned channel may be different.

For the purposes of providing context for embodiments of the inventionfor use in a communication system, FIG. 35 shows a base stationcontroller (BSC) 610 which controls wireless communications withinmultiple cells 612, which cells are served by corresponding basestations 614. In general, each base station 614 facilitatescommunications using OFDM with mobile and/or wireless terminals 616,which are within the cell 612 associated with the corresponding basestation 614. The movement of the mobile stations 616 in relation to thebase stations 614 results in significant fluctuation in channelconditions. As illustrated, the base stations 614 and mobile stations616 may include multiple antennas to provide spatial diversity forcommunications.

A high level overview of the mobile stations 616 and base stations 614upon which aspects of the present invention may be implemented isprovided prior to delving into the structural and functional details ofthe preferred embodiments. With reference to FIG. 36, a base station 614is illustrated. The base station 614 generally includes a control system620, a baseband processor 622, transmit circuitry 624, receive circuitry626, multiple antennas 628, and a network interface 630. The receivecircuitry 626 receives radio frequency signals bearing information fromone or more remote transmitters provided by mobile stations 616(illustrated in FIG. 35). A low noise amplifier and a filter (not shown)may be provided that cooperate to amplify and remove broadbandinterference from the signal for processing. Downconversion anddigitization circuitry (not shown) will then downconvert the filtered,received signal to an intermediate or baseband frequency signal, whichis then digitized into one or more digital streams.

The baseband processor 622 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 622 is generallyimplemented in one or more digital signal processors (DSPs) orapplication-specific integrated circuits (ASICs). The receivedinformation is then sent across a wireless network via the networkinterface 630 or transmitted to another mobile station 16 serviced bythe base station 614.

On the transmit side, the baseband processor 622 receives digitizeddata, which may represent voice, data, or control information, from thenetwork interface 630 under the control of control system 620, andencodes the data for transmission. The encoded data is output to thetransmit circuitry 624, where it is modulated by a carrier signal havinga desired transmit frequency or frequencies. A power amplifier (notshown) will amplify the modulated carrier signal to a level appropriatefor transmission, and deliver the modulated carrier signal to theantennas 628 through a matching network (not shown). Modulation andprocessing details are described in greater detail below.

With reference to FIG. 37, a mobile station 616 configured according toone embodiment of the present invention is illustrated. Similarly to thebase station 614, the mobile station 616 will include a control system632, a baseband processor 634, transmit circuitry 636, receive circuitry638, one or multiple antennas 640, and user interface circuitry 642. Thereceive circuitry 638 receives radio frequency signals bearinginformation from one or more base stations 614. A low noise amplifierand a filter (not shown) may be provided that cooperate to amplify andremove broadband interference from the signal for processing.Downconversion and digitization circuitry (not shown) will thendownconvert the filtered, received signal to an intermediate or basebandfrequency signal, which is then digitized into one or more digitalstreams.

The baseband processor 634 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 634 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 634 receives digitized data,which may represent voice, data, or control information, from thecontrol system 632, which it encodes for transmission. The encoded datais output to the transmit circuitry 636, where it is used by a modulatorto modulate a carrier signal that is at a desired transmit frequency orfrequencies. A power amplifier (not shown) will amplify the modulatedcarrier signal to a level appropriate for transmission, and deliver themodulated carrier signal to the antennas 640 through a matching network(not shown). Various modulation and processing techniques available tothose skilled in the art are used for signal transmission between themobile station and the base station.

In OFDM modulation, the transmission band is divided into multiple,orthogonal carrier waves. Each carrier wave is modulated according tothe digital data to be transmitted.

Because OFDM divides the transmission band into multiple carriers, thebandwidth per carrier decreases and the modulation time per carrierincreases. Since the multiple carriers are transmitted in parallel, thetransmission rate for the digital data, or symbols, on any given carrieris lower than when a single carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast FourierTransform (IFFT) on the information to be transmitted. For demodulation,the performance of a Fast Fourier Transform (FFT) on the received signalrecovers the transmitted information. In practice, the IFFT and FFT areprovided by digital signal processing carrying out an Inverse DiscreteFourier Transform (IDFT) and Discrete Fourier Transform (DFT),respectively. Accordingly, the characterizing feature of OFDM modulationis that orthogonal carrier waves are generated for multiple bands withina transmission channel. The modulated signals are digital signals havinga relatively low transmission rate and capable of staying within theirrespective bands. The individual carrier waves are not modulateddirectly by the digital signals. Instead, all carrier waves aremodulated at once by IFFT processing.

In operation, OFDM is preferably used for downlink and/or uplinktransmission between the base stations 614 to the mobile stations 616.Each base station 614 is equipped with “n” (≧1) transmit antennas 628,and each mobile station 616 is equipped with “m” (≧1) receive antennas640. Notably, the respective antennas can be used for reception andtransmission using appropriate duplexers or switches and are so labelledonly for clarity.

With reference to FIG. 38, a logical OFDM transmission architecture willbe described. Initially, the base station controller 610 will send datato be transmitted to various mobile stations 616 to the base station614. The base station 614 may use the channel quality indicators (CQIs)associated with the mobile stations to schedule the data fortransmission as well as select appropriate coding and modulation fortransmitting the scheduled data. The CQIs may be directly from themobile stations 616 or determined at the base station 614 based oninformation provided by the mobile stations 616. In either case, the CQIfor each mobile station 616 is a function of the degree to which thechannel amplitude (or response) varies across the OFDM frequency band.

Scheduled data 644, which is a stream of bits, may be scrambled in amanner reducing the peak-to-average power ratio associated with the datausing data scrambling logic 646. A cyclic redundancy check (CRC) for thescrambled data is determined and appended to the scrambled data usingCRC adding logic 648. Next, channel coding is performed using channelencoder logic 650 to effectively add redundancy to the data tofacilitate recovery and error correction at the mobile station 616.Again, the channel coding for a particular mobile station 616 may bebased on the CQI. In some implementations, the channel encoder logic 650uses known Turbo encoding techniques. The encoded data is then processedby rate matching logic 652 to compensate for the data expansionassociated with encoding.

Bit interleaver logic 654 systematically reorders the bits in theencoded data to minimize the loss of consecutive data bits. Theresultant data bits are systematically mapped into corresponding symbolsdepending on the chosen baseband modulation by mapping logic 656. Insome embodiments, Quadrature Amplitude Modulation (QAM) or QuadraturePhase Shift Key (QPSK) modulation is used. The degree of modulation maybe chosen based on the CQI for the particular mobile station. Thesymbols may be systematically reordered to further bolster the immunityof the transmitted signal to periodic data loss caused by frequencyselective fading using symbol interleaver logic 658.

At this point, groups of bits have been mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are then processed by space-timeblock code (STC) encoder logic 660, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at a mobile station 616. The STC encoder logic660 will process the incoming symbols and provide “n” outputscorresponding to the number of transmit antennas 628 for the basestation 14. The control system 20 and/or baseband processor 622 asdescribed above with respect to FIG. 36 will provide a mapping controlsignal to control STC encoding. At this point, assume the symbols forthe “n” outputs are representative of the data to be transmitted andcapable of being recovered by the mobile station 616.

For the present example, assume the base station 614 has two antennas 28(n=2) and the STC encoder logic 660 provides two output streams ofsymbols. Accordingly, each of the symbol streams output by the STCencoder logic 660 is sent to a corresponding IFFT processor 662,illustrated separately for ease of understanding. Those skilled in theart will recognize that one or more processors may be used to providesuch digital signal processing, alone or in combination with otherprocessing described herein. The IFFT processors 662 will preferablyoperate on the respective symbols to provide an inverse FourierTransform. The output of the IFFT processors 662 provides symbols in thetime domain. Each set of time domain symbols output by the IFFTprocessors 662 (each “frame”) is associated with a prefix by prefixinsertion logic 664. Each of the resultant signals is up-converted inthe digital domain to an intermediate frequency and converted to ananalog signal via the corresponding digital up-conversion (DUC) anddigital-to-analog (D/A) conversion circuitry 666. The resultant (analog)signals are then simultaneously modulated at the desired RF frequency,amplified, and transmitted via the RF circuitry 668 and antennas 628.Pilot signals known by the intended mobile station 616 may also betransmitted. These may for example be scattered among the sub-carriers.The mobile station 616, which is discussed in detail below, will use thepilot signals for channel estimation. Note that many examples have beenprovided above of how user content can be mapped to OFDM sub-carriers.In the particular example of FIG. 38, the different sub-band anddiversity channels are appropriately mapped to inputs of the IFFTfunctions. A channelizer (not shown) maps the symbols to the OFDMsub-carriers using any of the schemas described above.

Reference is now made to FIG. 39 to illustrate reception of thetransmitted signals by a mobile station 616. Upon arrival of thetransmitted signals at each of the antennas 640 of the mobile station616, the respective signals are demodulated and amplified bycorresponding RF circuitry 670. For the sake of conciseness and clarity,only one of the two receive paths is described and illustrated indetail. Analog-to-digital (A/D) converter and down-conversion circuitry672 digitizes and downconverts the analog signal for digital processing.The resultant digitized signal may be used by automatic gain controlcircuitry (AGC) 674 to control the gain of the amplifiers in the RFcircuitry 670 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic676, which includes coarse synchronization logic 678, which buffersseveral OFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationsearch window, which is used by fine synchronization logic 680 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 680 facilitates frameacquisition by frame alignment logic 684. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time domain to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 686 and resultantsamples are sent to frequency offset correction logic 688, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Preferably, thesynchronization logic 676 includes frequency offset and clock estimationlogic 682, which is based on the headers to help estimate such effectson the transmitted signal and provide those estimations to thecorrection logic 688 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 690. Theresults are frequency domain symbols, which are sent to processing logic692. The processing logic 692 extracts the scattered pilot signal usingscattered pilot extraction logic 694, determines a channel estimatebased on the extracted pilot signal using channel estimation logic 696,and provides channel responses for all sub-carriers using channelreconstruction logic 698. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency. Continuingwith FIG. 39, the processing logic compares the received pilot symbolswith the pilot symbols that are expected in certain sub-carriers atcertain times to determine a channel response for the sub-carriers inwhich pilot symbols were transmitted. The results are interpolated toestimate a channel response for most, if not all, of the remainingsub-carriers for which pilot symbols were not provided. The actual andinterpolated channel responses are used to estimate an overall channelresponse, which includes the channel responses for most, if not all, ofthe sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 700, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 700 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols

The recovered symbols are placed back in order using symbolde-interleaver logic 702, which corresponds to the symbol interleaverlogic 658 of the transmitter. The de-interleaved symbols are thendemodulated or de-mapped to a corresponding bitstream using de-mappinglogic 704. The bits are then de-interleaved using bit de-interleaverlogic 706, which corresponds to the bit interleaver logic 654 of thetransmitter architecture. The de-interleaved bits are then processed byrate de-matching logic 708 and presented to channel decoder logic 710 torecover the initially scrambled data and the CRC checksum. Accordingly,CRC logic 712 removes the CRC checksum, checks the scrambled data intraditional fashion, and provides it to the de-scrambling logic 714 forde-scrambling using the known base station de-scrambling code to recoverthe originally transmitted data 716.

In parallel to recovering the data 716, a CQI, or information sufficientto create a CQI at the base station 614, may be determined andtransmitted to the base station 614. As noted above, the CQI may be afunction of the carrier-to-interference ratio (CR), as well as thedegree to which the channel response varies across the varioussub-carriers in the OFDM frequency band. For this embodiment, thechannel gain for each sub-carrier in the OFDM frequency band being usedto transmit information is compared relative to one another to determinethe degree to which the channel gain varies across the OFDM frequencyband. Although numerous techniques are available to measure the degreeof variation, one technique is to calculate the standard deviation ofthe channel gain for each sub-carrier throughout the OFDM frequency bandbeing used to transmit data.

FIGS. 35 to 39 provide one specific example of a communication systemthat could be used to implement embodiments of the invention. It is tobe understood that embodiments of the invention can be implemented withcommunications systems having architectures that are different than thespecific example, but that operate in a manner consistent with theimplementation of the embodiments as described herein.

The MAC (media access control) layer is used to enable features in thephysical (PHY) layer in an OFDM air interface framework. Frames are aformat used to transmit data over the air interface between basestations and wireless terminals. A wireless terminal is any OFDM capablewireless device and may be fixed location, nomadic or mobile, forexample a cellular telephone, computer with a wireless modem, or PDA.Some types of information elements (IE) are included in the frame toprovide a structure within the frame for defining where downlink anduplink information are located within the frame.

In respect of a transmitter that uses the channelization approachestaught above, this may include the transmissions of one or more ofsub-band channel assignments and/or definitions, diversity channelassignments, and/or definitions, POPR signaling, and partial activationinformation. This may include the reception of one or more CQI, sub-bandvs diversity channel preferences, and preferred sub-band information.

In the embodiments described above, all of the diversity channels areassumed to be distributed in the frequency domain. In anotherembodiment, diversity channels are defined that use one or moresub-carriers, but with distribution in the time domain. There would becontent on select spaced OFDM symbol durations for a given time domaindiversity channel. Similar naming approaches can be adopted to definesub-channels and diversity channels using time domain diversity.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

What is claimed is:
 1. A method for operating a base station tocommunicate with one or more mobile stations, the method comprising:transmitting OFDM symbols using a plurality of sub-carriers within anOFDM band; the OFDM symbols collectively containing diversity channelsand sub-band channels, each diversity channel utilizing a plurality ofsub-carriers distributed across the OFDM band, and each sub-band channelutilizing a contiguous set of sub-carriers within the OFDM band; and atleast one of the OFDM symbols simultaneously including sub-carriersutilized by a sub-band channel and sub-carriers utilized by a diversitychannel.
 2. The method of claim 1, further comprising performing partialtree activation by: using a respective sub-channelization tree toorganize sub-channels into allowable channels for at least one ofdiversity channel definition and sub-band channel definition; for atleast one sub-channelization tree, activating a portion of thesub-channelization tree and sending information identifying the portion;and assigning channels from the portion of the sub-channelization tree.3. The method of claim 2 wherein activating a portion of thesub-channelization tree comprises activating a certain set ofconsecutive levels within the tree.
 4. The method of claim 2 whereinactivating a portion of the sub-channelization tree comprises activatinga respective set of consecutive levels within the tree for each of arespective set of at least one defined top node.
 5. The method of claim2 wherein activating a portion of the sub-channelization tree comprises:employing a first bitmap to identify a subset of nodes of thesub-channelization tree that are active.
 6. The method of claim 5further comprising: using a second bitmap to identify which nodes of thesubset of nodes are being assigned, and for each node being assigned,assigning a user identifier.
 7. The method of claim 2, furthercomprising: updating the partial tree activation from time to time. 8.The method of claim 7 wherein updating the partial tree activation fromtime to time comprises: sending update information only for segments ofthe tree that have changed.
 9. The method of claim 1, furthercomprising: persistently allocating a sub-band or diversity channeltransmission resource for VoIP traffic; and using one of two MCS(modulation and coding scheme) levels VoIP traffic by assigning one ofthe two MCS levels at a beginning of a call and only changing the MCSlevel if a significant change in a receiver's average reported CQI isdetected.
 10. The method of claim 9, further comprising: if a mobilestation reports a CQI that maps to a higher MCS than an operating MCS,decreasing a transmit power by an amount specified for the differencebetween the two MCS levels; and if the mobile station reports a CQI thatmaps to a lower MCS than the operating MCS, performing no poweradjustment.
 11. A base station for communicating with one or more mobilestations, the base station comprising: a processor coupled to a memory,the memory storing processor executable program instructions, which whenexecuted by the processor, cause the processor to: transmit OFDM symbolsusing a plurality of sub-carriers within an OFDM band; the OFDM symbolscollectively containing diversity channels and sub-band channels, eachdiversity channel utilizing a plurality of sub-carriers distributedacross the OFDM band, and each sub-band channel utilizing a contiguousset of sub-carriers within the OFDM band; and at least one of the OFDMsymbols simultaneously including sub-carriers utilized by a sub-bandchannel and sub-carriers utilized by a diversity channel.
 12. The basestation of claim 11, the processor executable program instructionsfurther causing the processor to perform partial tree activation by:using a respective sub-channelization tree to organize sub-channels intoallowable channels for at least one of diversity channel definition andsub-band channel definition; for at least one sub-channelization tree,activating a portion of the sub-channelization tree and sendinginformation identifying the portion; and assigning channels from theportion of the sub-channelization tree.
 13. The base station of claim 12wherein activating a portion of the sub-channelization tree comprisesactivating a certain set of consecutive levels within the tree.
 14. Thebase station of claim 12 wherein activating a portion of thesub-channelization tree comprises activating a respective set ofconsecutive levels within the tree for each of a respective set of atleast one defined top node.
 15. The base station of claim 12 whereinactivating a portion of the sub-channelization tree comprises: employinga first bitmap to identify a subset of nodes of the sub-channelizationtree that are active.
 16. The base station of claim 12, the processorexecutable program instructions further causing the processor to: updatethe partial tree activation from time to time.
 17. The base station ofclaim 16 wherein updating the partial tree activation from time to timecomprises: sending update information only for segments of the tree thathave changed.
 18. The base station of claim 11, the processor executableprogram instructions further causing the processor to: persistentlyallocate a sub-band or diversity channel transmission resource for VoIPtraffic; and use one of two MCS (modulation and coding scheme) levelsVoIP traffic by assigning one of the two MCS levels at a beginning of acall and only changing the MCS level if a significant change in areceiver's average reported CQI is detected.
 19. The base station ofclaim 18, the processor executable program instructions further causingthe processor to: if a mobile station reports a CQI that maps to ahigher MCS than an operating MCS, decrease a transmit power by an amountspecified for the difference between the two MCS levels; and if themobile station reports a CQI that maps to a lower MCS than the operatingMCS, perform no power adjustment.
 20. An integrated circuit forcommunicating with one or more mobile stations, the integrated circuitcomprising: circuitry configured to: transmit OFDM symbols using aplurality of sub-carriers within an OFDM band; the OFDM symbolscollectively containing diversity channels and sub-band channels, eachdiversity channel utilizing a plurality of sub-carriers distributedacross the OFDM band, and each sub-band channel utilizing a contiguousset of sub-carriers within the OFDM band; and at least one of the OFDMsymbols simultaneously including sub-carriers utilized by a sub-bandchannel and sub-carriers utilized by a diversity channel.